Fix field TypeError messages
Remove unused _fields
Make pylint pragmas more specific.
We won't have an admin, we don't need to carry these hints around.
Fix pylint warnings.
Move test tools into test.tools
Merge pull request #84 from edx/ned/remove-unused-_fields

Remove unused _fields
Merge pull request #85 from edx/ned/miscellaneous-cleanups

Miscellaneous cleanups
Merge pull request #87 from edx/ned/move-test-tools-into-test.tools

Move test tools into test.tools
Merge pull request #83 from edx/ned/fix-field-typeerror-messages

Fix field TypeError messages