Plugins work with CPU platform.  This involved separating the reference implementations of plugins into their own libraries.
Merge pull request #241 from peastman/master

Plugins work with CPU platform
All code is compiled with SSE enabled.  This eliminates errors with some compilers.
Merge pull request #243 from peastman/master

All code is compiled with SSE enabled.  This eliminates errors with some compilers.
Reference implementation of AndersenThermostat did not handle massless particles correctly
Merge pull request #244 from peastman/master

Reference implementation of AndersenThermostat did not handle massless particles correctly
Merge branch 'master' of https://github.com/SimTk/openmm
Merge branch 'master' of https://github.com/swails/openmm