Enable Ruby 2.0.0/Rails 3.2.12 build

* Move minimum version of Rails 3.2.x to 3.2.12 since this is the first version of 3.2.x to officially support Ruby 2.0.0
* Remove the exclusion for Ruby 2.0.0/Rails 3.2.0
Merge branch 'p-rcook-rails-3.2' into p-rcook-main