Limit lookup scope for private callbacks.

Background: Commit 71937c04ef introduced private callbacks, however, the use of "private_method_defined?" returns true all the way down the class hierarchy and thus causes trouble with a very common transition: Given an event "event :fail transitions_to :failed". If you don't explicitly define the "fail" event handler, "private_method_defined?" will still return true since Kernel#fail is defined for any object. Transitioning with "fail!" then causes a runtime error.
Add rake to gemfile to make test run under ruby 1.8.7
Fix warning in mocha
Remove obsolete VERSION file
Merge branch 'master' of https://github.com/svoop/workflow into svoop-master
issue58: switch from private to protected callback methods
Install dot on travis-ci to run tests for workflow diagram generation
Create temporary folders on travis-ci
Run travis-ci build with ruby 1.8.7 and 1.9.3
Issue #53 Add support for private callback methods again - but only in the immediate class
Provide a working example for #63 Recommendation for undoing an event
Using proper ActiveRecord method (update_attribute instead of update_attributes). Included tests.
Simplify test using attr_accessible, remove ActiveSupport::Concern for Rails 2 compatibility
Better test isolation in attr_protected_test
Separate the tests for newer Ruby, Rails and new features
Naming convention for test specific classes under test
Simplify the compare_states_test
Use update_column for newer Rails; ensure other dirty attributes are not saved on state change
Update the readme
travis-ci: temporary disable running 'rake test' for Ruby 1.8.7