Upgrade to Grunt 0.4.0 and Safari for Mac bug fix.

Upgraded the `Gruntfile.js` to be compatible with Grunt 0.4.x and added appropriate dependencies to `package.json`.  

Added a try/catch to fix Safari's issue with writing read only properties to pseudo elements.

Altered the `selenium.js`'s markdown function to skip report json files that do not exist instead of failing.  I've also added the lines to export a true markdown format file instead of html tables.  It works, but is currently commented out.

All qunit tests pass and I've added the new Mac benchmarks to the test readme.md.