Remove a lot of View display boilerplate by creating a generic function showView
Start on the settings page and delete account screen.

* Update the /settings screen with change password and sign out functionality
* Add /delete_account
* Add new auth-server functions to the fxa-client
* Allow the fxa-client to handle updating the Session state
* When visiting /, redirect to /signup

issue #254
Start to use accessor functions when working with session information.

* Add get/set/clear functionality for Session.
Session is now saved to localStorage to allow the user to reload the screen.

* Must use accessor functions to save data to Session
* Data stored in localStorage is automatically loaded into Session on startup.

fixes #310
Users must be signed in to see the settings and delete_account pages.
Notify the Session.channel of user status changes from within fxa-client.js

* Reduces the number of places this needs to be done.
Various cleanup:

* Update the settings test to handle unverified emails.
* After password change, sign the user in again.
* Get rid of unused dependencies.