Colorized error output

Colorized the error output in response to #292. 

I removed the excess `~`s from the error log. Seems to look cleaner without them.

without `~`
![screen shot 2014-02-20 at 11 58 32 pm](https://f.cloud.github.com/assets/458421/2227926/07fea522-9ad0-11e3-8bd3-60318504e71c.png)

with `~`
![screen shot 2014-02-20 at 11 51 58 pm](https://f.cloud.github.com/assets/458421/2227922/067a887e-9ad0-11e3-9d54-876419f6c49f.png)