Added support for "make install" from pull request #10 by bobben
Fixup kdtree documentation with missing VlDistanceHistInt
Invert sign of Histogram Intersection distance

For Histogram Intersection, the higher the distance the more accurate the match:
d(A,A) > d(A,B) when A != B.
For sake of simplicity instead of rescale the computed distances one can just
invert the sign:
d(A,A) < d(A,B) when A != B.