Test runner does not minify, so don't test minified version
Add an option to keep closing slash in singleton tags

If ``keepClosingSlash`` is set to ``true`` in options, closing singleton slash
will be preserved. This is important for HTML5 being minified, since in HTML5
closing slash is not optional and affects the DOM significantly.

Closes #76.
Merge pull request #122 from kotnik/closingSlash

Add an option to keep closing slash in singleton tags
Merge pull request #121 from kotnik/devease

Test runner does not minify, so don't test minified version
Switch to Grunt.
Drop Node.js 0.6 support.
Add banner to dist files.