feature(client): Flash messages

issue #891
fix(build): Use the custom version of Modernizr in prod, not the full version.

fixes #949
refactor(test): Less auth-server logging for travis tests!

Only display errors.
chore(l10n): fix supported locales script to print correct missing strings
Merge pull request #984 from mozilla/issue-949-future-of-the-past

fix(build): Use the custom version of Modernizr in prod, not the full version.
Merge pull request #924 from mozilla/issue-891-flash-message

feature(client): Flash messages
Merge pull request #998 from mozilla/fix-supported-locales

chore(l10n): fix supported locales script to print correct missing strin...
Merge pull request #1004 from mozilla/less-auth-server-logging

refactor(test): Less auth-server logging for travis tests!
feature(client): debounce resend button clicks.

* Send emails on the first and forth attempt. Shake the success message otherwise.
* After the forth attempt, hide the resend button for 5 minutes.
* Change the name of `.error-shake` to `.shake`.
* Update `.shake` to cause 8px of movement, not 100px.

issue #885