Added support for SubmitButton and SubmitButtonFor
Added Button and ButtonFor.
Renamed SubmitButton to SubmitInputButton.
Added SubmitButton and SubmitButtonFor.
Moved ButtonHellper into Helpers.
Added support for BeginButton and BeginButtonFor.
Moved SubmitButtonExtensions into ButtonExtensions because they share the same code.
Added support for BeginSubmitButton and BeginSubmitButtonFor.
Added support for CheckBoxListItemLabel and CheckBoxListItemLabelFor.
Updated version to 3.1.0