trying out Herb's cython stuff
x
bring in final version of cython code from Herb
fix problem with yN dimensionality and get heli_opt running with it
clean up some indexing in DiscreteProperties
updated cython version of VortexRing from Herb
cleaned up vortex test case
add timeit comparison of cython vs python version of vortex code as a test
update setup.py to build the cython extension
add the C source file in case cython is not available
add numpy to setup.py
remove utility script