small typo in checkpointreporter.py true --> True
 Changes to be committed:
	modified:   checkpointreporter.py

there is a small typo in checkpointreporter.py in openmm. line 81 has:
self._own_handle = true
instead of True.
Merge pull request #600 from kmdalton/master

small typo in checkpointreporter.py true --> True