Polished the Community section

![openra-community](https://f.cloud.github.com/assets/756669/2116847/c5de7014-90a2-11e3-8a8f-f525cd3c86e3.png)

Gave the page a more generic title as @ScottNZ suggested and easily recognizable SVG icons as @pchote requested. Chose https://commons.wikimedia.org/wiki/Tango_icons because they are clean, scalable and require no attribution.