SD-277 As user I want to be able to set an avatar with an image from local storage
Add support for cropping while uploading image.
fix(validation): return errors with predefined keys

eg for unique we return `{'email': {'unique': 1}}`

SD-317
fix(validation): add custom response to rest of used validators

SD-317
fix(users): make password minlength match ui
SD-277 retrieve user avatar on get
SD-277 Add test for cropping
SD-277 fix flake8 style error
SD-277 fix flake8 style error deja-vu
Update .travis.yml
fix(cache): force cache revalidation
SD-277 simplify the way avatar is stored on the user
SD-277 the problem is between the chair and the monitor
SD-277 fix failing test
SD-277 remove unneeded print statement.
Merge remote-tracking branch 'adrian/master'

Conflicts:
	app.py
fix(tests): add some tolerance to crop file size test
SD-315 : _created and _updated fields display invalid date