Add About Us page

make some progress on issue nairobilug/nairobilug.or.ke/issues/16
![menu](https://f.cloud.github.com/assets/3141711/1289180/8b54c7bc-301d-11e3-8008-462883ed9035.png)

Basically took the content of @nj3ma [October LUG Meetup](https://github.com/nairobilug/nairobilug.or.ke/blob/master/content/october_nairobilug_meetup.md) and turned it into an about us page. 

Revisions and contributions welcome.