Fix JS error checking via Hound

Since enabling JSCS, Hound CI reviews for PRs
which contain JS code changes have been failing
to complete.

ThoughtBot have advised us that the JSCS
checker is in beta and that we should simply disable it.
They noted that ESLint has received a better response
from other testers so we might want to look
at that instead.

 - Use the legacy 'esnext' option only instead of both
   'esnext' and 'esversion' for compatibility with JSHint v2.8.x
   on Hound and developers who have the current stable version
   installed locally.

 - Remove the 'maxErrors' option from the JSCS config, as this
   prevents use of the '-x' option to autofix files which is
   a little annoying.

Fix ubuntu dev install docs

Focus input field after creating a new annotation

The previous method of scrolling a newly created annotation
into view in the sidebar resulted in the input field for
the new annotation losing focus.

Note that only top level annotations have an 'id'
attribute set on the corresponding HTML element.
It might make sense to change this in future although
it would add an extra binding. For now I've just noted this.

When a new annotation card was added, the sidebar tried
to focus it but this failed because the sidebar iframe
itself did not have focus.

When a new annotation is created, first focus the sidebar
in the Annotator host and then let the sidebar focus the
input field.

 * Remove unnecessary use of the $timeout service which
   triggers a root scope digest.

Split Travis build up using matrix

This allows `gulp build` to run without devDependencies installed.

Implement tools to enable Chrome extension sourcemaps

Hound CI is currently using JSHint v2.8.0 which
uses 'es3', 'es5' and 'esnext' config options instead of
the 'esversion' option in v2.9.0 and later.

When the H client is served from a local URL (eg.
chrome-extension://ID/scripts/foo.bundle.js), the original
source URLs and source maps are not accessible
to Sentry.

Enabling source maps for extensions is done in three steps,
the first two of which are implemented in this commit:

 1. Changes to the crash reporting to transform local URLs
    into filenames when reporting exceptions.

    This results in URLs for source files in Sentry
    reports which are independent of where the files
    are served from
    (eg. chrome-extension://ID, moz-extension://ID...)

 2. A Gulp task that uploads JS bundles and their associated
    sourcemaps to Sentry using the Sentry API.

    The assets are uploaded to Sentry using just the filename as
    the URL, so the source files and source maps are correctly
    matched up with the transformed URLs produced by the changes
    in (1).

 3. Configuring CI builds to run the Gulp task from step (2).

This commit makes use of ES2015 template strings in
upload-to-sentry.js, so the JSHint file has been adjusted
accordingly.

Remove undocumented /api/annotations endpoint

Convert fuzzy timestamp formatting functions to JS

In preparation for changing the formatting of breakpoints,
convert this module to a plain CJS module in JS.

Clean up application config/settings

This way it's possible to run `gulp build` without installing the
development dependencies.

Standardise and improve log output for all servers

Upgrade to Pyramid 1.6

Add a test and fix a parameter for queries

Refactor and add tests for annotation editor toolbar commands

Move API token model to app

Previously all modified lines in a block were replaced in one
call to replaceText() when applying block formatting, which
lost the selection.

This rewrites the command to transform each line separately
which preserves the selection.

 * Separate the logic for transforming the input field
   from the logic for actually reading the state of
   the input field and applying changes.

   This enables testing of the commands without
   instantiating the component.

   Toolbar commands are functions which take
   the current state of the input field and return
   the updated state.

 * Add tests for the individual commands and use
   of the commands in the markdown editor.

Switch to codecov

Make hound run jscs

Enable admins to activate users

Add an "Activate" button next to users on the /admin/users page so that
admins can activate user accounts.

Some refactoring to avoid code duplication between activating by users
clicking on an activation link and admins clicking the new activate button:
move the code that actually activates the user onto the User model where
both views can call it.

Packaging cleanups

Convert <markdown> component to JS and add basic tests

This commit moves a couple of helper tasks for developing the frontend
into the gulpfile, and also improves the automatic installation of
dependencies and building of assets.

All that is now required to get a running development server (with built
frontend assets) from a fresh checkout of the repository is:

    make dev

Subsequent runs of `make dev` will ensure the JavaScript and Python
dependencies are up-to-date but will not rebuild the assets unless they
are either explicitly cleaned,

    make clean dev

or the developer runs the gulp `watch` task independently (recommended).

Similarly, from a fresh checkout, it should be possible to run the test
suite simply by running:

    make test

Note that this commit removes `gulp-cli` and `karma-cli` from the
package dependencies -- these packages are not intended to be installed
in a software distribution, although they can both be installed globally
to assist with easier dispatch of gulp/karma tasks if needed:

    npm install -g gulp-cli karma-cli

Fix tags autocomplete dropdown CSS

Speed up npm dependency checking when running 'make dev'

When package.json changes, use 'check-dependencies' to do
a lightweight offline-only check of whether the installed
packages match the versions specified in package.json
before running the much slower 'npm install' to actually
install any missing dependencies.

7fff01e changed the annotation cards from <article> to <annotation>.
This seems to break the CSS of the tags autocomplete dropdown
(particularly: the width is too short) unless the <annotation> has
display: block;

Fixes #3007.

Ensure request session is correctly committed in non-web contexts

Fix docker build