Cleanup

* Removed Finder (Mac OS X) .DS_Store files.
* Added a .gitignore to ignore the Finder files.
* Set executable permissions on build scripts.
Start of HTML5 element support

* Map HTML5 elements to their implicit roles.
* NOTE: this does not yet to all conditional checks.
Full HTML5 Element Support; Documentation

* Support HTML5 element roles, including containment checks.
* Update max Firefox version.
* Convert README to Markdown.
* Version bump and update XPI.
Documentation cleanup
Merge pull request #2 from matatk/master

Minor Cleanup