Fixed failure with checkbox
Moved placeholder to InputField, added additional validation attrs
Added pattern attribute
Made HTML5 attributes mixins for form-fields
Merge branch 'feature/html5-validators' of github.com:toscawidgets/tw2.forms into feature/html5-validators

Conflicts:
	tests/test_widgets.py
	tw2/forms/widgets.py
Merge branch 'develop' into feature/html5-validators
Added docstrings, TODO items; fixed typo and pep8
Include classes for all major HTML5 input types.
Un-HTML5ify the base class from unused attributes

Also clean up the class definitions and re-order them.
Yay, easy
Demos.
Merge pull request #25 from toscawidgets/feature/html5-validators

New HTML5 input types