Bug 816666: Update server and prod push docs.
Fix Bug 823908: Preserve locale for tabzilla redirects.

- Ensures that if a locale is used with the old tabzilla URL it will 
  keep that locale through the redirect.
- Fixes a test that assumed the en-US locale was activated (and broke
  as a result of the tabzilla test activating a different one).
Add GA tracking to dl button on /new. bug 824370

Add firefox/new-a.js to /firefox/new page. Mimic GA tracking from /new-b.
Merge pull request #560 from mozilla/firefox-new-b-tracking-update

Add GA tracking to dl button on /new. bug 824370
Merge pull request #542 from pmclanahan/bug-816666-fix-pushing-prod-docs

Bug 816666: Update server and prod push docs.