Rename FxUI to FxAccountsUI
Ensure that the UI flow always returns a result
Merge pull request #49 from ferjm/fxa_module

Rename FxUI and send UI result back to chrome
Update with :alive's comments & start to fix tests.

* Ensure function expressions have names.
* Place `'use strict';` at the top of files.
* Cache elements after querying for them in the DOM.
* Fix the set password tests.
* Add vim hints at the top of each file.
Updates based on @borjasalguero's feedback.

* Add importElements to utils.js, importElements in modules.js proxies to there.
* Use `exports` to export FxaModuleErrors
* Rename function names in fxam_manager to use fxamm_ instead of fxa_module_manager
* In fxam_overlay.js and fxam_error_overlay.js, check this.initialized instead of checking for elements to see if the module is initialized.
* In fxam_modules.js, prepend fxam_ to each of the function names