Fixes resolving to db_field from class field name, in distinct() query.
Merge conflicts resolved.
Removed merge trackers in code, merged correctly now.
Merge remote-tracking branch 'upstream/master'
importlib does not exist on Python 2.6. Use Django version.
update pickling test case to show the error
Merge pull request #327 from elasticsales/pickle-error

Document is not picklable before it is saved
Fixed pickle unsaved document regression (#327)
Merge pull request #326 from mitar/importlib-python26

importlib does not exist on Python 2.6. Use Django version.
Updated Changelog
Version bump
Merge branch 'master' of github.com:MongoEngine/mongoengine
Updated requirements for test suite
Fixing django tests for py 2.6
Added get image by grid_id example
Documentation cleanup (#328)
Upgrade doc fix (#330)
More upgrade clarifications #331
Fix py3 test
dont simplify queries with duplicate conditions