cmake / installation dir of the pyopenvdb python module

[Drew Whitehouse]

Hi, I'm currently making an openvdb package for http://spack.io (check it out, it's very cool) and I've run into a small issue with the location of the pyopenvdb.so. Shouldn't it be installed into <prefix>/lib/python<version>/site-packages instead of the current <prefix>/lib/python<version> which is generally reserved for python itself?