Removed Disqus extension from master, since it has its own repo now
Removed FacebookComments extension from master, since it has its own repo now
Removed FacebookLike extension from master, since it has its own repo now
Removed Editable extension from master, since it has its own repo now.

Pinging @Rixbeck
Removed Authenticate extension from master, since it has its own repo now.
Pinging @GawainLynch
Removed GoogleAnalytics extension from master, since it has its own repo now.
Removed Helloworld extension from master, since it has its own repo now.
Removed ImportWXR extension from master, since it has its own repo now.
Merge branch 'master' of https://github.com/bolt/bolt