Interactor

* [FEATURE] Add around hooks

* [ENHANCEMENT] Add TomDoc code documentation

* [FEATURE] Remove "magical" access to the context through the interactor
* [FEATURE] Manage context values via setters/getters rather than hash access
* [FEATURE] Change the primary interactor API method from "perform" to "call"
* [FEATURE] Return the mutated context rather than the interactor instance
* [FEATURE] Replace interactor setup with before and after hooks
* [FEATURE] Abort execution immediately upon interactor failure
* [ENHANCEMENT] Build a suite of realistic integration tests
* [ENHANCEMENT] Move rollback responsibility into the context

* [FEATURE] Halt performance if the interactor fails prior
* [ENHANCEMENT] Add support for Ruby 2.1

* [FEATURE] Roll back when an interactor within an organizer raises an error
* [BUGFIX] Ensure that context-deferred methods respect string keys
* [FEATURE] Respect context initialization from an indifferent access hash

* [BUGFIX] Allow YAML (de)serialization by fixing interactor allocation