remove debug messages from cpp python wrapper
move numpy call import_array() to the cython module
add comments and rename cpp potential wrapper
fix a bug in array.h

_allocated_data was not being set properly.

setup.py sets the cflag -DNDEBUG by default.  I figured out how to turn
that off by redefining the environment variable OPT.  e.g.
OPT="-g -O3" python setup.py build_ext -i