Fixes for OSX 10.9 Mavericks

Fixes for the issues reported by users in #10 (`CFRunLoopRun': undefined method `call')`

Use Ruby 1.8 path since the default Ruby in Mavericks (2.0) doesn't have osx/foundation.

Also, people using Mavericks should update their rubycocoa to latest here: http://sourceforge.net/projects/rubycocoa/