Add support for bower package manager

bower register jquery.gritter git://github.com/jboesch/Gritter.git
Update README.markdown
Update bower.json
Gritter Accessibility Changes

Adding in role to the main gritter item wrapper, as well as changing the
close div to a link tag to allow it to be readable, as well as able to
be closed via keyboard
Gritter Accessibility Changes

Adding in return false on the click function instead of the javascript
void in the link href.
Merge pull request #45 from heitzke/master

Gritter Accessibility Changes
Merge pull request #43 from peters/master

Add support for bower package manager
Merge remote-tracking branch 'remotes/jboesch-original/master'