Added "removed" feature type

"Removed" features and "deprecated" features look the same except the tooltip content is different.

BUG=#100

![screenshot from 2014-07-17 13 28 34](https://cloud.githubusercontent.com/assets/634478/3612118/b1368004-0da5-11e4-9ecf-b1b3656f69fb.png)

Done.