starting
Add from_openmm and to_openmm functions, addressing issue #105
work in progress
add to/from dataframe, and some convenient methods to get specific atoms/residues/chains
some documentation
add doctest skip instructions
docs
pdb3 naming conventions for the columns, and make bonds optional in to_dataframe
add note that indices are zero based
correct typo'
set the index as the serial
make serial the index column instead
Merge pull request #125 from rmcgibbo/topology

Make Topology more convenient