fix(client): No longer automatically sign in existing users on signup.

* Show them the "Account already exists. Sign in" error message instead.

fixes #877
refactor(test): Use a single function to create email addresses.

* TestHelpers->createEmail will create a restmail address
* Update ad-hoc email address creations to use this
* Add TestHelpers->emailToUser to get the user from the email address.

fixes #1050
fix(client): Do not show Fx for Android marketing material if completing sign up on B2G or Fennec.

issue #1041
Merge pull request #1051 from mozilla/issue-1050-generic-email-create

refactor(test): Use a single function to create email addresses.
test(intern): Update Intern to 1.7.0
Merge pull request #1061 from vladikoff/int170

test(intern): Update Intern to 1.7.0
fix(l10n): normalize locale when fetching client.json

Fixes #1024.
Merge pull request #1052 from mozilla/issue-1041-no-marketing-mobile-firefox

fix(client): Do not show Fx for Android marketing material if completing sign up on B2G or Fennec.
Merge pull request #1063 from mozilla/issue-1024-normalize-locale

fix(l10n): normalize locale when fetching client.json
refactor(view): use shortened url for Android marketing banner

Fixes #1036.
Merge pull request #1064 from mozilla/issue-1036-android-marketing-url

refactor(view): use shortened url for Android marketing banner
Release v0.12.0
Let's lint the app/test/ files
fix(tests): Fix the jshint errors and warnings in all of the tests.

* Remove all of the remaining `global: *` declarations
* Remove or comment out all veriables that are "defined but never used"
* Use dot notation where it is "better" (very subjective)
* Make unreachable code reachable.
A couple more tweaks from Shanes meta-PR
fix(tests): Add a missing semicolon.
Merge pull request #1072 from mozilla/molint-moproblems

Molint moproblems

Travis is green. I'm merging. Thanks for this effort @pdehaan!
fix(client): Fix the "Sign in" link on `/confirm_reset_password` if the user is in the force auth flow.

* The user should be returned to /force_auth instead of /sign_in

fixes #926
chore(tests): Add tests to ensure the correct client.json is returned under a variety of circumstances.

* all uppercase language
* all lowercase language
* uppercase region
* uppercase language
* multiple regions supported, only language specified
* unsupported region returns root language
* no Accept-Language header sent
* Three part locale

issue #979
Merge pull request #987 from mozilla/issue-877-existing-user-signup

fix(client): No longer automatically sign in existing users on signup.