git rm test/spec/SpecEventEmitter.js

EventEmitter is already tested here:

  https://github.com/Gozala/events/tree/master/tests
implement SIP.EventEmitter.prototype.off
test/spec/SpecSession.js: define .logger on the constructed Session

This prevents tests from failing
  due to an artificially constructed Session's logger being undefined
    since the Session no longer has a logger by way of being an EventEmitter
src/Session.js: the following methods correctly return `this`:

- failed
- rejected
- canceled
- accepted
- terminated
- connecting
src/Subscription.js: .failed() correctly returns `this`