Make pending show as yellow

This is a common idiom in ruby land at least (rspec, cucumber, etc), so I borrowed from that because Cucumber.js output seems to do the same.  I also added an undefined class to the pending css block because that is how Cucumber marks them when it spits out the suggested step matchers on first run.

![screen shot 2014-05-15 at 1 11 32 pm](https://cloud.githubusercontent.com/assets/106/2987958/08694a56-dc54-11e3-97b9-3b57828cf6c2.png)