Revert "add ruby instance methods for using the mexican hat wavelet"

This reverts commit 7330699446977524a81a1ac78d0a2f5c8de4ee63.
Revert "add support for mexican hat wavelet in pHash"

This reverts commit fa0ed121fd1b0c67a44aa983efd06294a634476d.
Merge pull request #40 from westonplatter/pr-37-reverse

pull request to back off mexican hat wavelet