Changing Firefox brand+logic for WebPlatform

Basics:
* Adjusting README, merging rebase from oauth branch
* fxa-content-server-i10n is installed through bower
* Add our own sign_up validation event handlers
* Improved extension without overwriting events hash map
* Overriding signup marketing ad specific to Firefox/Mozilla

Account pre-existence validation form events:
* Check for existing user and add notice on the form
* Follows convention to setCustomError on form field when username is invalid
* Setting in place webservice call service
* Including shell script to check user details through PHP in scripts/getuserinfo.sh