Prevent partner's province from updating

- change permit_params in app/admin/partner.rb
- add attr_readonly for province in partner model
- add test in partner model spec to check for attributes after update
Prevent partner's province from updating (cont'd)

- rename the test for the update method (to avoid awkward wording)
- add a test to demonstrate that the partner model accepts a province
  upon create
Merge pull request #213 from azangru/272_partners_update_controller

Prevent partner's province from updating (OSRA-272)
OSRA-272 #resolve