Small text change README
fix deprecation warnings for ActiveRecord 4
Add Gemfile to test against Rails 4.0.0.beta1

All tests pass, but there's a ton of deprecation warnings.
Fix remaining Rails 4 deprecation warnings

All tests are now passing on Rails 3.0 through 4.0.0.beta1 without
deprecation warnings.
Merge branch 'rails4' of git://github.com/adammck/ancestry into adammck-rails4