Add Grunt support.

Combine and minify CSS and JS files.

Also, include the version from package.json in the CSS and JS filenames and increase the expires headers for those files to 1 year.
css/style.css: Remove unused selector.
css/style.css: specify default font size/line height.
Switch to classes.
index.html: remove unused class.
Resize img/opg.png to 256x122.
Add plugins.js from html5 boilerplate.
SyntaxHighlighter: fix a few CSS issues.

* add missing unprefixed `border-radius` property
* `background-color: none` isn't valid so use `transparent` in its place
Add Ubuntu regural font generated with FontSquirrel.
Specify X-UA-Compatible.

Though the visitors using IE should be only few, it's a good practice forcing the last IE version.
Losslessly compress img/ubuntu.png.

Before: 1642 bytes
After:  1552 bytes
style.css: change the order of selectors; no functional changes.
Move common property to a new selector.
Convert favicon.png to ico.

This way it should work in all browsers.