Add more settings tests and differ tests depending on if isFirefoxOS

Test Plan:
- Run http://localhost:8092/test/test.html
Add UI tests for settings pane

Test Plan:
- Run http://localhost:8092/test/test.html
Move out react testing from other unit tests

Test Plan:
- Run http://localhost:8092/test/test.html
Enable tr and bn for localization tests

Test Plan:
- Run http://localhost:8092/test/test.html
Add translations for v1.1 features

Test Plan:
- None
Add translated strings for Bengali

Test Plan:
- Run tests, make sure everything passes again
Fix runlint script so it doesn't reference a file which no longer exists

Test Plan:
- Run tools/runlint
Specify react prop types. Fixes #22.

Test Plan:
- Run tests, play with app
Grabbing playbackSpeed set by UI
Replaced playbackSpeed refs
Merge branch 'playback-speed' of https://github.com/farezv/khan-academy-fxos into playback-speed