Add a tabs example to the pattern library
Turn forgot password button back into a button
Improve tab styles on the authentication forms

Previously the active tab would be red, which could be confused with our
red anchor text and make the other tab look disabled. The new design
makes all text gray but adds an "active" border below the button.
Use border only on active nav-tabs item
Merge pull request #1352 from hypothesis/improve-tabs

Improve usability of sheet tabs
Fix viewFilter._arrayMatches()

The filtered copy list was not assigned back to the variable and
accidently we were comparing the value.length instead of the filter.terms.length
to check whether all tags have matched or not.
Merge pull request #1368 from hypothesis/search-callback-routing-cleanup

Search callback routing cleanup
Fix the tag facet
Refactor and isolate identity, auth, and session

Introduce a new module on the frontend called `h.identity` which
abstracts the interaction between the main application and the
authentication system using the `navigator.id` API introduced by
Mozilla as part of Persona / BrowserID. In our case, the we submit
the authentication assertion as a query parameter in our token
URL. This is designed to flexibly accommodate different auth needs
by intepreting the assertion differently and using a different
identity module to return whatever type of grant is needed depending
on the authentication mechanisms in place on the back end.

On the back end:

- Introduce a dependency on a brand new library, pyramid-oauthlib, to
  make this code cleaner and more modular.
- Simplify our session by removing multiple signin code that was not
  ever fully realized; personas are no longer explicitly maintained in
  the session by application code.
- The Pyramid SessionAuthenticationPolicy is put into place as part of
  h.auth.local. A SessionGrant is configured as the default grant type
  for integration via pyramid-oauthlib. This is what interprets the
  assertion sent in our token request. For other use cases, this might
  be a real BrowserID assertion or a session or refresh token of some
  other kind. This assertion is just the CSRF token our forms have been
  returning already.
- `h#includeme` and `h#create_app` got some superficial simplification.
- `h.api#authorize` handler for annotator-store authorizations now uses
  `request.effective_principals` instead of the session, so it doesn't
  care how the user is authenticated
  - Headers are now passed through on `Store` sub-requests so that both
  the annotator auth token and the session work for store authorizations
  which gets us close to cookie-less API auth!
  - `Consumer` class is moved into `h.auth.local`, removing the SQL
  requirement for core `h` and replacing it with just the requirement to
  register an `IConsumer` implementer.

On the front end:

- Break hypothesis.js into hypothesis.js and hypothesis-auth.js
- Move session and auth modules into this auth package
- Clean up the module dependency imports
- Add an identity module to the auth package with `navigator.id` API
- Significantly refactor `AppController`
  - Use the `identity.watch()` API to listen to login/logout from the
  active identity module
  - Clean up the login/logout state management a bit
    - Resolve a promise when the API service discovery happens
    - Stop using 'session', which becomes a detail of hypothesis-auth
  - Put much less on the scope from the controller
    - `scope.initUpdater` -> `initUpdater`
    - `scope.reloadAnnotations` -> `initStore`
    - `scope.session` -> replaced by `id`
    - Sorts and views are set in the markup
    - `AuthController` no longers needs to know about `model`, `sheet`,
    `sorts` or `views`
  - Isolate the form models
    - The auth directive now creates an isolate scope so that we're not
    leaking the form models all over the place
    - Stop using the inherited `$scope.model` means prevents submitting
    `persona` as a form parameter by accident
- blocks.pt#auth-tabs becomes auth.html
  - Easy to override with `config.override_asset()` in Pyramid
  - Keeps the forms inside the isolate scope of the auth directive
- The content of the sheet moves inside blocks.pt#auth
  - Nothing outside this knows or cares anymore that the sheet has tabs
  - Places where we want to request login use `identity.request()`
  rather than having to get at the root scope. The `authorize` event
  that this broadcasts is an internal detail of the auth pacakage.