Cleanup

This branch mitigates the problem discussed in #14, although it doesn't attempt to solve it directly.

Instead, I've done three things:

* added the [inherited_resources](https://github.com/josevalim/inherited_resources) gem, which allows us to drop almost all of our current controller code;

* switched the default template language from ERB to [Haml](http://haml.info), which allows us to drop code from almost every view; and

* created multiple new partials, which allows us to DRY up our views.

I have not converted the layouts from ERB to Haml, but all other views have been converted.

There is some duplication in the views which I have not attempted to remove.