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

A couple of related improvements to how we build the Dockerfile:

1. Don't invalidate the Python dependencies layer just because
   `package.json`, `gulpfile.js` or `scripts/` changed.
2. Use a prebuilt node-sass binary. The prebuilt binaries supplied by
   the node-sass project aren't compatible with Alpine Linux (which uses
   musl-libc rather than glibc).
3. Make some small tweaks to the gulpfile so we can build just the
   assets needed for the web application (i.e. skipping the extension).

This code is in pretty poor shape. Some lint violations
were easily fixed, others will require larger refactoring
of the code. Before that can be done the existing behavior
needs test coverage. For the moment this commit suppresses
the lint violations.

As an initial step towards cleaning up the annotation
editor component, convert it to JS and add basic tests.

The conversion was automated using
[decaffeinate](https://github.com/decaffeinate/decaffeinate)
with a small amount of subsequent cleanup.

The tests are very basic at the moment and cover
just the read-only/editing states and rendering
of markdown and LaTeX

Remove angular-animate dependency

This reduces the Angular bundle size by about 30KB.

There are no references to ng-{enter, leave, move} or
the other hooks that I could find.

angular-animate was added in fdf132efe7d56de34633451c159b05460769a259
but the mentioned CSS classes no longer exist.

Add "bouncer" support to Chrome extension

Postgres documents

Streamer work queue

Remove unnecessary dependency on YAML

Fix form button background gradient

Remove unused '...' which were originally variable
arguments to the compass 'linear-gradient()' mixin.

Now we are just using the linear-gradient() CSS function
however so the '...' was never expanded, resulting in
invalid CSS.

New front-end build system based on Gulp