'class' isn't highlighted at the end of a word

Without this, the character string `class` is highlighted when appearing at the end of another word. For example:

![screen shot 2014-07-14 at 14 09 32](https://cloud.githubusercontent.com/assets/1965587/3571008/1f3fc628-0b58-11e4-93e2-a61aef1d08c3.png)

Where the correct behaviour would be only the final line being highlighted.