Upgraded Rails from 3.2.13 to 3.2.15. Removed unneeded "~>" gem numbers in Gemfile. Upgraded Ruby to 2.0.0.

 1. Upgraded Rails from 3.2.13 to 3.2.15.
 2. Removed 3 unneeded "~>" gem numbers in Gemfile so they could float.
 3. Upgraded Ruby from 1.9.3 to 2.0.0.