Remove PolymorphicManager from Cowry Models.

Specifying PolymorphicManager is not needed because it's the default manager
for PolymorphicModels.
Add country list in select box
Merge pull request #239 from benkonrath/small-cleanups

Remove PolymorphicManager from Cowry Models.
Merge pull request #238 from gannetson/select-country

Select country