Bug 1072493 - Add initial testing suites

Supersedes #2770 to move the tests and improve the docs.
I suggest we combine:
* `Hovering over the header nav widget opens submenu`
* `Clicking Persona link opens new window`
* `Logging in with Persona for the first time sends user to registration page`
into a single test.
The assertions made in the first two tests can easily be moved into the `completePersonaLogin` util method.
Less duplicated code to maintain = happy coders.