[Fix Bug 748503] Rewrite for Nightly Redesign
Merge pull request #890 from Sancus/master
Enable GA tracking on new /firstrun/b5/ URL. Bug 873899.
Bug 772952 - Security error when searching using Tabzilla
Merge pull request #900 from kyoshino/bug-772952-mixed-content

Bug 772952 - Security error when searching using Tabzilla
Bug 874903: Update Tabzilla to CDN URLs.

Also fix styleguide Tabzilla docs.