Improved consistancy

Lol not really i changed one line, that was distracting :)
Force wtforms dependency version
Merge pull request #540 from psykzz/patch-1

Improved consistancy
Merge pull request #544 from Jaza/master

Fixes #543: Import of wtforms _unset_value needs to change to unset_value
Update travis.txt
Change bool_formatter() to be backward compatible with bootstrap2
Merge pull request #545 from xelez/master

Change bool_formatter() to be backward compatible with bootstrap2
Add widget_format field to DateTimeField to allow modifying datetime format from form_widget_args
fix spacing issue with previous commit
change __all__ to include DateTimeField
add comments to new DateTimeField
attempt to fix "Not a valid datetime value" error
add "format" parameter for string to date formatting
add formats back to __init__
remove "formats"
Merge pull request #549 from pawl/master

Allow Changing DateTimeField's date-format using form_args
Fixed #457, generally improved multi-PK models handling and inherited models
Python 3 fixes
move 'data-date-format' to form_widget_args and allow overriding hardcoded kwargs
remove widget_format from comments