dont simplify queries with duplicate conditions
fix guide link
minor typos
Update django.rst
FileField should pass db_alias to GridFSProxy in __set__ call
fix __set_state__
if `dateutil` is available, use it to parse datetimes

In particular, this picks up the default `datetime.isoformat()` output, with
a "T" as the separator.
add some tests
fix change tracking for ComplexBaseFields
Moved pre_save after validation and determination of creation state; added pre_save_validation where pre_save had been.
Added missing reference in __all__.
Added tests for pre_save_validation and updated tests for pre_save to encompass created flag.
Added pre_save_validation to signal list in documentation.
Improved signals documentation and some typo fixes.
Fixed :module: reference in docs and added myself to authors.
Update upgrade.rst

Added docs for the new function: clean()
Merge pull request #354 from Jiequan/patch-1

Update upgrade.rst: Added docs for the new function clean()
Merge pull request #334 from ryanwitt/patch-1

fix link to guide from tutorial
Added Ryan to AUTHORS #334
Added Jiequan to AUTHORS #354