Add expansion for PSR

Made official the expansion of `PSR`.
Merge pull request #120 from saji89/patch-1

Add expansion for PSR
Added FAQ link for new question
Removed Gemfile requirement for 2.1.4
Also bumped version requirements for HTML Proofer after they fixed the irc:// issue.
Updated the SaberDAV domain.
added Revive Adserver as member
Merge pull request #133 from lsmith77/Revive

added Revive Adserver as member
Drive by: ignore .bundle
Update to latest gems, add jekyll-redirect-from
Use jekyll-redirect-from plugin, now that we can.

Fixes #107
Fix download-instead-of-redirect issue.

See jekyll/jekyll-redirect-from#37
See #108
More robust build script file handling (mkdir -p)
Add build script PSR page stubs.
More idiomatic (and slightly cleaner) Ruby in _build
_build script cleanup:

 * Fix all the wonkiness around translations and extras introduced by recent _build script updates.
 * Standardize translation order so that it's consistent everywhere.
 * Clean up pt_BR urls, redirect from all the other valid variations.
 * Suppress "translations" on the extras pages, since they don't work anyway.
 * Use clean urls for extras pages too. This is 2014. There's no need for .html.
 * Fix wonky # in titles of the generated PSR-4 stubs.
Do case-insensitive filesystems a favor and remove the old pt-BR before adding one that's pt-br :)
Update built PSR page stubs.
Annnd a bunch of whitespace fixes.
Remove unnecessary local variable.