add Travis-CI support
Require Forwardable
Tell respond_to? to look at more than just public methods

In ruby 2.0 respond_to? returns false for protected methods.

http://tenderlovemaking.com/2012/09/07/protected-methods-and-ruby-2-0.html
tweak travis config
Merge pull request #5 from prognostikos/master

Ruby 2.0 compatibility + Travis-CI support