Defaulting to homebrew and trimming down the RVM calls

- set autolibs to use homebrew
- removed the rvm reload, as the source call on line 23 is the recommended way to reload after an installation
- removed the second autolibs line, as it is a repeat of the option passed on line 22
Specify the patch level for ruby to match the Rakefile
Merge pull request #9 from jessmartin/patch-1

Minor improvements to OS X build script