Some light cleanup and refactoring.

* Add a unit test harness for is_this_your_computer
* When the user authenticates, set them as seen.
* In storage.js, Use an object to store the usersComputer info instead of arrays for developer grok.
* Add storage.js->clearUsersComputerOwnershipStatus for testing.
* Clean up user.js->logout a little bit.
* Completely clear localStorage between every test.
* Add tests to check for when the user should see the "is this your computer" screen.