Changed Promise API to conform to execute-method pattern
added unscheduled status management
Changed Promise API to conform to execute-method pattern
added unscheduled status management
added spec for long chains
added factory methods
added Rescuer class
changed `then` signature to accept rescuers
added on_success method
removed unnecessary Rescuer class
implemented chain management on fulfill
first working implementation (not thread safe yet)
first really working implementation (not thread safe yet)
thread safe implementation
Merge branch 'refactor/promise' of https://github.com/jdantonio/concurrent-ruby into refactor/promise

Conflicts:
	lib/concurrent/promise.rb
	spec/concurrent/event_machine_defer_proxy_spec.rb
	spec/concurrent/promise_spec.rb
Renamed Promise.fulfil to fulfill
Merge pull request #23 from jdantonio/refactor/promise

Refactor/promise