Make armrest emit events

* Emits a 'response' event for each request.
* This event emits reponseCode, requestDuration, method, url
	which can be used to plot graphs
Refactor code
Use util.inherit to inherit EventEmitter
Emit two events -
	* HttpResponse - For HTTP responses, status codes
	* NetworkError - For Network timeout error, connection error
Cleanup tests
Revert to a single response event
Update tests
Merge branch 'events'
Ran fixjsstyle on code
Bumped the version to v2.3.2