Introduce end event. Exit the CLI after end.

Exiting the CLI on complete may not allow for browsers
launched via WebDriver to close. The new end event will
fire when browsers (if any) have shutdown.
agentManager -> allAgents
Fix bug that ignores a request to launchBrowsers.
agentManager -> allAgents (for unit test)
Merge pull request #27 from reid/quit-process-on-end

Quit process after browsers quit, introduce end event