fix(client): Enable back button functionality when visiting `/`.

* use history.replaceState instead of history.pushState when redirecting from `/`.

fixes #763
Merge pull request #897 from mozilla/issue-763-redirect-on-startup

fix(client): Enable back button functionality when visiting `/`.

@nchapman gave the r+, I rebased. Merging.
feature(client): Add a `/cookies_disabled` page.

* Add a cookies_disabled template, view, and test. Provides a link to SUMO to get help as well as a "try again" button.
* Split off most of the code from main.js into lib/start-app.js so that it can be tested.
* Split off config loading into its own modules, lib/config-loader.js so that it can be shared.

fixes #738
fix(build): Fix the typo when copying fonts.

fixes #907
fix(client): Fix disappearing error messages when toggling password visibility.

fixes #903
fix(client): Correctly handle the THROTTLED error from fxa-client.js->signUp

fixes #905
chore(client): Email addresses should not be bold.

fixes #902
feature(client): Add backoff protocol error strings.

* Use the 201 errno as the indicator for `server busy`
* Change `Service unavailable` to code 998, this is a client side only number.

fixes #484
Merge pull request #908 from mozilla/issue-907-typo

fix(build): Fix the typo when copying fonts.
Merge pull request #898 from mozilla/issue-484-backoff-buster

feature(client): Add backoff protocol error strings.
Merge pull request #884 from mozilla/issue-738-cookies-disabled

feature(client): Add a `/cookies_disabled` page.
Merge pull request #911 from mozilla/issue-902-delicate-settings-email

chore(client): Email addresses should not be bold.
Release v0.10.0
Merge pull request #909 from mozilla/issue-903-dissappearing-error

fix(client): Fix disappearing error messages when toggling password visibility.
Merge pull request #910 from mozilla/issue-905-wtf-throttled-error

fix(client): Correctly handle the THROTTLED error from fxa-client.js->signUp
Intern 1.6 Update
Merge pull request #869 from vladikoff/in16

Intern 1.6 Update
feature(client): Check email verification tokens before rendering.

* URL parameter validation for `/complete_reset_password` and `/verify_email`
* Add validate.js for a central place to do validation.
* Update form to validate email addresses using validate.js
* Validate emails, tokens, and codes on the client.
* Handle errors sent by the server that says uid or code is bad.
* Handle expired tokens by giving the user an opportunity to resend the email.
* Add unit and functional tests for corner cases.

fixes #788