Update all dependencies to their latest versions
Update `Gruntfile.js`

* Remove `grunt-contrib-uglify` as it is no longer needed.
* Remove extra commas.
* Fix typo in comment.
Remove obsolete JSHint options
Update jQuery to v1.11.0
Losslessly compress images
Add images to filerev
Use protocol relative URL for the web font
Update `index.html`

* Remove no longer needed JSHint global (`YT:false`).
* Fix typos in comments.
Fix validation errors.
Add `grunt-html-validation` plugin.

Also add a test target which runs the needed tasks.
Add Travis CI support.
README.md: add a devDependencies badge.
Add grunt-uncss.
Base64 encode the background images.

-2 HTTP requests and CSS size is +1.5KB of what it was before grunt-uncss (8.47KB minified without gzip).
Use the shorthand `font` property.
Be more explicit with the `background` property.