Rename methods

Rename method `test_get` to `test_get_status_code`, both in classes
`EntityTestCase` and `EntityIdTestCase`. This rename is performed for two
reasons:

* The new names are more descriptive.
* The new names allow one to more precisely select which test should be run when
  using nosetest's `-m` regex option. Formerly, issuing `nosetests -m test_get`
  would cause methods `test_get` and `test_get_unauthorized` to run. Now, one
  can issue `nosetests -m test_get_status_code` and run a more precise set of
  tests.