Remove unused SESSION_CHANGED event

Minify production build and fix prod build in non-ES6 browsers

Ensure that NODE_ENV is set to 'production' when building the client for
release and thereby ensure that the JS and CSS is minified.

We are not currently transpiling client code using Babel, so this
doesn't work with our minifier or older browsers.

This event was fired by the `session` service but not listen for by any
other module.

Use new profile update endpoint for dismissing sidebar tutorial

Explicitly update vinyl-fs's graceful-fs dependency to v3.0.11.

graceful-fs v3.0.8 had a dependency on an internal Node module which no
longer exists in Node v7.

See https://github.com/gulpjs/gulp/issues/1843

Make `store.profile` an object containing `read` in preperation for the
upcoming changes where we will use the update profile endpoint for
updating a user's preferences.

Adding client metric tracking for interactions with annotations

In preparation for adding a profile update endpoint, the name of the
route for fetching the profile was renamed to 'profile.read'.

See https://github.com/hypothesis/h/commit/a3d45a4a4abb5b7b6f899eade5186820340a545c

Verify userid after connecting to WebSocket

Listen for the 'whoyouare' reply to the 'whoami' request sent after the
WebSocket connects and log a warning if the userid does not match the
logged-in user for any reason.

Show annotation counts on page.

Show annotation count on the page, so that users don't have to open to sidebar to know how many annotations are in the page.

Fixes: https://github.com/hypothesis/product-backlog/issues/129

Use access token to authenticate WebSocket connections

* master:
  Remove auth => session dependency

Exchange access token and fetch profile via API when a grant token is provided

 * Clarify that the service list augments rather than replaces the
   default list which consists of the public Hypothesis service.

 * Document the keys of objects in the _services_ array

Send a "whoami" request [1] after connecting to query the authenticated
user ID for the WS connection.

This makes it easy to check that authentication for the WS worked as
expected by inspecting the frames of the connection in the devtools.

[1] http://h.readthedocs.io/en/latest/realtime/#whoami

Supply the access token to the WebSocket via a query param.

This method is used to send the token because the WebSocket constructor
does not allow setting custom headers. See
https://github.com/hypothesis/product-backlog/issues/154 for context.

An alternative that was tried initially was embedding a username and
password in the URL via `wss://user:password@host/` syntax but that
turned out not to be supported by IE/Edge and required the server to fail
the initial request with a 401 response.

Fixes hypothesis/product-backlog#126

* master:

Remove auth => session dependency

 * Start the clock just _before_ the access token exchange
   occurs, otherwise the client will incorrectly add the delay between
   the server sending the token and the client receiving it to the
   expiry timestamp.

 * Use performance.now() instead of Date.now() so that expiry checks
   are not affected by system clock changes.

   performance.now() is supported on IE >= 10 and all modern browsers.

These tests stub the $http service rather than relying on the mock
$httpBackend from Angular mocks because that makes it easier to work
with native Promises.

When the user is on a page using 3rd party accounts but is not logged
in, they will not have an access token.

In this case, the 'authority' argument provides a way for the service to
determine which authority-specific groups and preferences should be
included in the returned profile.

Document the 'services' config param which the host page may provide to
the client.

Implement access token and profile retrieval for embedders of the client
that provide an OAuth grant token as part of the client's configuration.

For a page embedding Hypothesis configured to use a 3rd-party account,
the start up flow for the client is:

 1. Read service configuration from 'services' array in settings

 2. Exchange grant token from service config for an access token
    using the `POST /api/token` endpoint

 3. Fetch profile data using `GET /api/profile` endpoint

On startup, the app reads the service config and then switches between
either the cookie-based auth implementation or the OAuth-based auth
implementation.

In future, the cookie-based auth implementation will be removed in favor
of OAuth-based auth for first-party accounts as well.

Simplify the "auth" service and remove the dependency on the
"session" service. This will make it possible to introduce a "store" =>
"session" dependency in future in order to support fetching the user's
profile from the access token-authenticated /api/profile endpoint
instead of the cookie-authenticated /app endpoint.

The 'auth' service depended on 'session' for three things:

 - Being able to call `session.load()` in order to retrieve a CSRF
   token. This token is not needed for the `GET /api/token` endpoint
   following https://github.com/hypothesis/h/pull/4322

 - Calling `session.logout()`. This is fixed by removing the
   `auth.logout()` endpoint and changing the caller to call
   `session.logout()` directly instead. `session.logout()` in turn
   calls `auth.clearCache()` to clear cached API tokens.

 - Determining the current user ID in order to invalidate
   the cached token when that changes. The logic to clear the
   cache has instead been moved to the session service.

This commit also adds additional tests for session logout.