Issue 99 share room tests

Fixes #99, testing various aspects of share room models and collections.

These tests include ones which verify the password-protected content provisions, including features that are currently surfaced only in the public share rooms, like forgetting the password.

This does not include tests for the intricate effects that being or not being logged in has on the remembered roster of public share rooms.  I figure that's the purview of integration testing.  (I've covered the salient details in [the remembering section](https://github.com/SpiderOak/SpiderOakMobileClient/wiki/Functional-Operation#wiki-Remembering) of the functional operations document, for use in integration testing.)

This also includes provisions to address #182, by which tests can be insulated from incidental localStorage state. Use helper.suspendLocalStorage(), typically in beforeEach(), to run tests with a clean localStorage, and subsequently invoke helper.resumeLocalStorage() to reestablish the prior localStorage state.