Mavericks (Ruby v2) adjustments

Hi!
Loved your ruby template! I'm using a fork for my own workflows :)

The thing was for me that it didn't work quite well with Ruby v2 on mavericks, which makes sense since Mavericks wasn't around 5 months ago, hehe. Lucky for me, it helped me to understand a lot more about ruby, gems, environment, and specially native extensions.

I've made chances to make it work in Mavericks, though I don't know if it will work correctly on previous versions, specifically with Ruby 1.8.7.

Basically I: 
* changed require for require_relatve in the bundler setup require
* changed bundle call for /usr/bin/bundle to have the gems that use native extension to work correctly on Ruby that gets shipped with Mavericks
* changed the documentation to match both this changes

Hope you like it!
Cheers