Simplified API prototype

(Turns out you can't reopen a pull-request after a force-push..... original was #11 )

Updated version of my original pull request. Keeps the existing Tasty API, but changes internals and adds a new API. I did split it into 3 commits, it's probably easiest to look at each of them seperately.

As a short description of the interactive mode, it executes all golden tests. If golden == actual, nothing interesting
happens. If golden is missing (e.g. new test), it show the actual value and asks whether to accept that.
Similar for golden /= actual, it shows the diff and asks whether to accept/reject the new value. Interactive mode only works/tested on linux right now, but could be easily extended to other OS.