trying some new algorithm for the template match

 (see #138 for discussion)

The numbers the matchTemplate function gives us were not reliable for
large needles, so I tried something else and I'm now calculating the MSE
of the area and the scene part found matching.

The MSE I map to a comparable percentage number, following
http://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio example

I also extended .travis.yml to run the tests and added a dozen more
test cases found during deployment