Initial implementaiton of an in memory undo stack.
Fix lint and add a verifyObject test.
Simple integration of undo stack with launch_server workflow.
Pass undo stack through the supervisor to launch_server.  Supervisor will rewind the stack if launch_server fails.
Fix lint.
Initial implementation of load balancer cleanup.
Make sure undo is passed all the way through, and serialize calls to add_to_load_balancer so that the undo stack works as expected with multiple load balancers where the first may succeed.
Test rewind of empty stack.
Fix test docstring.
Document error handling and stop on error behavior.
Fix docstring and improve test by checking explicitly that verified_delete is only pushed onto the undo stack after create_server succeeds.
Test that launch_server doesn't push onto the undo stack if create_server
fails completely.
Test that load balancers don't push onto the undo stack unless they succeed.
Test that coiterate is properly passed to InMemoryUndoStack and skip some unecessary test harness.
Merge branch 'master' into auto-172-launch_server-cleanup
Fix lint.
Don't care about which logger is passed to verified_delete.
Log the error that cause stack rewinding informationally.
add_to_load_balancers should always return a deferred.
Merge pull request #325 from rackerlabs/auto-172-launch_server-cleanup

Auto 172 launch server cleanup (ready for review)