Remove outdated/incorrect notes about adding languages in the README.
Merge pull request #143 from mozilla/language-as-site

Language as a Site Groundwork
New admin mixin for adding translation helpers to the change form.
Simulate the admin popup to show the original english version of the content.
Add links next to translatable fields.
Plug the TranslatableMixin into the page/form admin classes.
Use the translation admin for links as well.