GitLab

Updated tests of serialization of CustomNonbondedForce, though test omits comparison of interaction group sets since I couldn't figure out how to do that.

Removed redundant overload of == operator in AssertionUtilities.h. Removed extraneous version check for serialized integrators and state. Updated unit test to include more details. 

Completed support for serialization of all integrator types. Modified Assertion utilities to allow ASSERT_EQUAL to work on strings. Updated unit tests for testSerializeIntegrators. 

Support for serialization of Integrator base class, and two derived classes: LangevinIntegrator and VerletIntegrator. Also added support for python serialization via a single deserializeIntegrator()