Fix has_key deprecation warning.
PEP8
Add wrapper_class option to Field.
Merge branch 'wrapper_class' of git://github.com/VMitov/django-crispy-forms into dev

Conflicts:
	crispy_forms/bootstrap.py
Adding tests for Field wrapper_class special attribute
Updated docs for Field wrapper_class and HTML5 attrs
Indenting for better readability
Updated CHANGELOG and CONTRIBUTORS