EMD (Earth Movers Distance) mex interface

This code is the mex interface for computing Earth Movers Distance between signatures and is based on the Y. Rubner's C Implementation.
(http://ai.stanford.edu/~rubner/emd/default.htm)

For building the mex file you should have setup your mex build environment. Invoke "build_emd" for building and "demo_emd" for a small test.