Merge pull request #86 from pitr-ch/minor

Convenience methods for Obligation and add_observer returning self
Updated brittle specs for Supervisor restart strategies.
Updated brittle Supervisor #count#stopped spec.
Updated brittle Exchanger with timeout spec.
Updated brittle Observable specs.
Updated brittle TimerTask specs.
Updated brittle Supervisor specs.
Merge pull request #88 from jdantonio/refactor/brittle-specs

Refactor brittle specs
Add Delay#reconfigure method

allows to replace the block evaluating to the value with new one
only if a delay is still incomplete?
Fix configuration to be thread safe

by replacing ||= operator with Delay instances