Setup a default bundler cache for ruby 2.0.0 (default ruby)

Precompile and install a default set of gems. The [compile script](https://github.com/hone/hammer-ruby-default-cache) is built to do rails 3, rails 4, nokogiri, puma, unicorn, and bcrypt-ruby. As we collect more data from heroku, we can get a better picture of what gems to presetup, but this is a good starting point.

This cuts getting started bundle install times if everything hits to < 1s.

```
Bundle completed (0.74s)
```