feat: Translated TOS/PP text!

* Pull translated TOS/PP text from repo using bower, convert to HTML using grunt.
* Handle TOS/PP serving on the backend using new routes: `<locale>/legal/*`
* If `locale` is not specified or cannot be found, use a fallback template.
* Return 500 error with error message if a fallback template cannot be found.
* Front end requests localized TOS/PP partials from the backend, on demand, and inserts them into the DOM. partial vs full html rendering is determined by `Accepts` header.

Issue #634
feature(l10n): translate tos/pp
fix(client): Ensure the client specifies a language when requesting TOS/PP templates.
fix(server): Redirect with locale name that abide understands.

* Abide expects URLs to use `-` as the separator, we were redirecting to URLs with `_`.
fix(build): Normalize TOS/PP filenames to use the `_` separator.

* All other l10n files use the `_` separator, use them here too.
fix(tests): Ensure a real locale is used for TOS/PP template requests.
fix(build): Use lowercase extensions on output files in marked.
Merge pull request #674 from mozilla/issue-634-import-tos-pp

Localized TOS/PP!
feat(client): updating js client to 0.1.17
Merge pull request #822 from vladikoff/jsc0.1.17

feat(client): updating js client to 0.1.17
feat(client): Add support for "can_link_account" Desktop Channel message.

This message is called in the Desktop context before a "sign in" or
"sign up" to check with the Desktop browser whether another user has
previously logged in to the browser. If one has, Desktop presents
a warning to the user, giving her an opportunity to cancel the operation.
If the user cancels, we cancel the underlying "sign in" and "sign up"
operation with the auth server.
Merge pull request #726 from mozilla/issue-682

feat(client): Add support for "can_link_account" Desktop channel message.
refactor(css): remove unused class
Merge pull request #826 from mozilla/issue-652-allcaps

refactor(css): remove unused class
feature(client): Disable the submit button while auth server requests are outstanding.

* In Form based views, add beforeSubmit and afterSubmit. beforeSubmit disables form submissions until the submission completes and afterSubmit is called.

fixes #751