Add not-all-numbers validation to username

Also, fixes "alphabet" to be "letter" in the error messages for
validations (Fixes #137)
Get rid of better_errors, don't really need it.
Restructure search component in the header.
Reduce .recent-post-avatar margin-right.
Use WAD to cache bundles in travis. Closes #109.
Try to fix WAD.
Allow FakeWeb to connection to CodeClimate.
Get rid of message_bus.
Remove message-bus from vendor.js.