Added NumpyFile as numpy array image reader in image.py.
Added tests on scale and offset in PatternGenerator's __call__ before doings ops.
Merge pull request #17 from mjabri/master

Added NumpyFile array reader and associated tests on scale and offset in PatternGenerator that allow bit-for-bit copies of a specified Numpy array (or any other supplied pattern, such as an image, that doesn't need scaling).