Merge pull request #9 from peastman/master

Bug fixes to use of shuffle
Merge pull request #11 from peastman/master

Improved infrastructure for integrators
add support for long long shuffles
Merge pull request #13 from proteneer/master

Add support for long long shuffle
Created API and reference implementation for ring polymer contraction
Merge branch 'master' of https://github.com/peastman/openmm
Created CUDA implementation of ring polymer contraction
Created OpenCL implementation of ring polymer contraction
Created Python API for ring polymer contraction
Merge pull request #14 from peastman/contraction

Implemented RPMD ring polymer contraction