Hook up the new FxA JS client.

* Update bower config to fetch the new FxA JS client.
* In postinstall npm command, install the FxA JS client's dependencies and do a build so the client is available.
* Create a light wrapper around the FxaJSClient to reduce boilerplate code.
* Use the fxa-js-client from the bower install, get rid of picl-gherkin
Password reset and complete password reset screens.

issue #121