Adding compatibility for ruby 1.9, also making the repo functioning with bundler

Hi,

since I had to replace authorization with something roughly compatible, I chose permit_yo, but quickly ran into a problem with it's ruby 1.9 compatibility - you're using the instance_variables array which returns strings in 1.8 and symbols in 1.9. I patched it by using the activesupport method instance_variable_names (and added activesupport as a dependency which shouldn't be a problem for a rails plugin.

I also updated the dependencies and cleaned up a few things. I also added a gemspec to allow using the gem as a git dependency in bundler. I'm trying to follow current best practices with these changes.

This gem kinda looks unmaintained, but I'm sending the pull request nevertheless. If you want me to take over the gem, please let me know, I'd gladly take it.