title: Authenticate Jenkins CI for Github private repository
body: <p>I'd like for Jenkins to automagically fetch data from my private repository hosted on Github.
  But I have no idea how to accomplish that task.. Tried the documentation, generating ssh-key for jenkins user and all what I can see is: "unable to clone the repo". I've checked URLs - they are valid.</p>
  
  <p>Any clues, maybe you know some docs/blogs/whatever which are describing this kind of stuff?</p>