Prepare releasehistory.rst for 0.15.0 release
Release History
===============
-Development snapshot
-====================
+0.15.0 - Restraint forces
+=========================
- Add radially-symmetric restraint custom forces (`#336 <https://github.com/choderalab/openmmtools/pull/336>`_).
- Copy Python attributes of integrators on ``deepcopy()`` (`#336 <https://github.com/choderalab/openmmtools/pull/336>`_).
- Optimization of `states.CompoundThermodynamicState` deserialization (`#338 <https://github.com/choderalab/openmmtools/pull/338>`_).
+- Bugfixes (`#332 <https://github.com/choderalab/openmmtools/pull/332>`_, `#343 <https://github.com/choderalab/openmmtools/pull/343>`_).
0.14.0 - Exact treatment of alchemical PME electrostatics, water cluster test system, optimizations
