This is a major revision that removes the `method` parameter of `match_template` and uses a new normalization method.
Note that the example result is different with this new normalization.
* Change Cython function to take names of correlation method instead of numbers representing the methods.
* Use alternate formula for `template_norm` of 'norm-corr' method, but note that both formulas need to be checked for correctness.
* Add note that `match_template` output has a different shape than the input image. This needs to be fixed before merging.
* Change 'Sigma' to 'Sum' in docstring to avoid confusion with standard deviation.
* Other minor changes for readability.
Andreas Mueller