Refactoring of the main file

Added functions for handling messages and added tests for testing
robot responses.
Refactored "get job"
Tested with real Jenkins server

Added api-mock for Jenkins API and tested with real Jenkins server.
All tests updated.

Fake api server is not used in tests for now. I'm using it for testing
hubot script locally. To run jenkins fake api server
```
/node_modules/.bin/api-mock test/jenkins_apiblueprint.md
```
Fixed bug in build job response text

Hubot script was using non-existing key from response.