Delightful 404 page

Took a first pass at fleshing out a delightful 404 page to replace the current pages default 404.

Dropped in the google 404 widget to hopefully provide some help locating content for now, but may be able to leverage the search API to do something slick here in the long run.

Thoughts on something charming / witty / fun?

![screen shot 2013-10-16 at 12 30 46 pm](https://f.cloud.github.com/assets/282759/1345987/847718e6-3699-11e3-8997-2f79b5b1acc6.png)

Fixes #65.