Provide support for _html suffixed translations

If the locale file has a key_html or key.html version, it will be used
over the non-html version. This lets the user provide things like icons
within the breadcrumb.

An example end result:
![Home crumb with icon](https://cloud.githubusercontent.com/assets/218121/2885573/d09ca15c-d4c6-11e3-883f-e7306c891eeb.png)