Use the t() function in JavaScript

Draft (work in progress) -- AWAITING PEER REVIEW
Steps: 

- in your module/theme identify where you need to use text in Javascript
- instead of just writing English text, wrap the text in Drupal.t(), like Drupal.t('Drupal is awesome')
- when running the module/theme Javascript, check the text ends up on the translation form (admin/config/regional/translate) - make sure to run the code with a foreign language page
- translate the string
- test that it works on the output