Refactor UsersController#create

* Simplify controller action
* Extract service classes
Revert "Stop using user agent to detect mobile devices. Use a media query and yepnope to load the appropriate css and customizations."
downgrade pg, pg 1.7 is buggy it is being fixed, we need to wait for the next release
see: https://groups.google.com/forum/#!topic/ruby-pg/5_ylGmog1S4
FIX: Staff should be able to see PMs
FIX: can grant titles to regular users. Guardian initializer needs current_user, not the target user.
Show estimated reading time near summarize button.
Version bump to v0.9.7.7
Use COALESCE in case there are no posts in a topic
Version bump to v0.9.7.8
Add retry to migrate_word_counts
improve bench script
Disable ddl transactions for realz!
added international amazon domains to matcher
changed . to \.
Upgrade font-awesome to version 4
Re-apply with fixes: Stop using user agent to detect mobile devices. Use a media query and yepnope to load the appropriate css and customizations.
attempt to fix amazon item descriptions
better revision history
:scissors: scoped for Rails 4 compat
remove unused diff_engine class