Bug 887777 - Set up the first few tests for keyboard suggest

Fix for [#887777](https://bugzilla.mozilla.org/show_bug.cgi?id=887777). This adds some structure to the keyboard suggestions where we can add some more tests in the future. It mocks the worker and has a simple interface to talk to the IM.

The extra lines in latin.js are there because we had an undefined global hanging around that we crashed upon in tests.