Test under ActiveRecord 3.2
Use String#constantize instead of Kernel.const_get

Kernel.const_get barfs on namespaced constants. Since this is in the AR adapter,
ActiveSupport is present and constantize will do the right thing.
Omit belongs_to association information for omitted relationships
Merge pull request #29 from zerowidth/belongs-to-fixes

belongs_to association fixes
Merge pull request #23 from iangreenleaf/test_3_2

Test under ActiveRecord 3.2