other cython modules can now use array_wrap_np
add cython function to convert pele::Array into numpy array
remove parallel connect rountines

It's better to do the whole double ended connect in parallel using
pele.concurrant
added inverted power potential (incomplete)
make the git revision visible from within pele

setup.py identifies the git revision and saves it in a created file
pele/version.py

the git revision can be found by

    import pele.version
    print pele.version.git_revision
started neighbor_iterator class implementation
cell list reset function added
added compare neighbours function
added are_neighbors function and build cell neighbor list function
corrected arguments to AASiteType in pele/angleaxis/aatopology.py
saved symmetry operations as angle-axis rotations as well as matrices in pele/angleaxis/rigidbody.py
implemented cell list next function
added MolecularCluster cluster class and associated minperdist classes/routines
minor reformatting
add some comments
started build atom neighbors list
added simple water cluster test
added virtual destructor
added fortran cell_lists file to use as template
wrapped inversepower, added cpp test (incomplete)