Add Rails 4 gemfile.  Update Travis CI matrix to include Ruby 2 and Rails 4
Fix assorted Rails 2.3 and 3.0 test failures.  Hide validator and validator tests for Rails 2.3.  Use :get on errors if :messages isn't available (Rails 3.0)
Convert symbol to string to support Ruby 1.8.7.  Exclude Ruby 2.0 and Rails 2.3.x from matrix.
Merge pull request #35 from petergoldstein/feature/rails_4_travis_integration

Travis CI - Rails 4, Ruby 2, and get existing matrix to green