Add a test suite using a publically-available image corpus

[tokenrove]

Since people are actually using this code, I have some plans for improvement. Before that can happen, we need a test suite so we can evaluate the accuracy and efficiency of the existing implementations and ensure that there are no regressions.

[saurabheights]

Uploading an image for test suite. This is single intensity image, all pixels at grayscale value 128.

My view is since the image has no blurred edges, the output should be indeterminate(or well-focused) instead of ill-focused. This image represents the use-case when an image has many blocks with no change in intensity, lets say an image of chessboard with each square of size 64x64.