Update Zones to remain in alphabetical order

We had been doing this until recently, but "Firefox Marketplace" and
"Add-ons" ended up out of order.

Dropping "Persona" from the homepage feels strange, but we have the
following bug open for solving this long term.

https://bugzilla.mozilla.org/show_bug.cgi?id=946777
Merge pull request #1728 from openjck/alphabetize-zones

Update Zones to remain in alphabetical order