Support <label><input></label> style for checkboxes and radio buttons

[mbrowne]

As posted on the OOCSS forum: https://groups.google.com/forum/#!topic/object-oriented-css/m5m_SbCLoCc
The issue I had was with checkboxes and radio buttons...as long as my HTML was like the examples, it was fine, but sometimes I like to wrap my tag around the checkbox or radio button, e.g.:

<label>
  <input type="checkbox"> Check me
</label>

And if I want to use the style shown in the docs, I just need to add the hanging-indent class:

<input type="checkbox" id="checkbox1">
<label for="checkbox1" class="hangingIndent"> Check me</label>

If anyone has any other ideas I think it would be good to discuss them, but in any case I think both styles of HTML should be supported.

I'm happy to update the documentation file as well if this pull request is accepted. Thank you.

[mbrowne]

I have now updated the documentation for this as well:
mbrowne@f6775d2
If you're going to accept this pull request, just let me know and I'll create a pull request for that commit.