Fix "skip to main content" not focusing for screen readers

### Story ###
- https://www.pivotaltracker.com/story/show/71503760

### Notes ###
- using [this blogpost](http://blog.paciellogroup.com/2013/02/using-wai-aria-landmarks-2013/) as a reference, added <code>role="main"</code> landmark to main <code>#bonnie</code> div for desired "skip to main content" behavior