Improving error handling:

- The device now replies with a partially valid JSONWireProtocol response (no
sessionId).
- Controller methods now automatically inject things like the sessionId and
check the response from the device
- All status codes used come from status.js
fixing unit test
fixing sessions test to comply to JSONWP
final fixes and compliance with the new error handling pattern
adding test to prove correct error handling
a bit nicer code, put multiple it inside describes
ohai, this is js, not python
Merge pull request #37 from santiycr/master

Improved error handling