Accessibility improvements

I added a directive that will keep the element it is attached to up to date with the check status - updating the icon and color to display contextually relevant information.

In this PR I have also updated some outdated dependencies to work around an old karma/phantomjs issue - unrelated but should be safe.

Finally, I changed the Stashes icon from `fa-database` to `fa-briefcase` - I would like to gather consensus but the aliasing on the database icon at that size detract from the look of the page in my opinion.

This PR would partially resolve #80 
When a client/check has status 2, the style will be 'critical' and not 'danger' (since Sensu define 2 as 'critical').

I think an easy solution would be to simply add something like `if (style === 'critical') { style = 'danger'; }` before calling the updateGlyph() function.

What do you think?