Fix: sass blows up when bundled with scss-lint

I got the same error as @joaomilho in issue #39 (Cannot be used as a gem). I was able to fix the error by moving the sass monkeypatching files out of the global load path and into lib/scss_lint. Please see http://weblog.rubyonrails.org/2009/9/1/gem-packaging-best-practices for the basis.