Merge pull request #3 from jonathantompson/master

added bicubic and lanczos filtering for image.warp function.
added mean parameter to gaussian, guassian1D and laplacian functions.
Added an openmp c-based version of gaussian.  Using 12 cores it is about 300x faster on a 640x480 gaussian image.  I verified that it gives the same result (within floating point roundoff).