compute fep examples
====================

* `CH4hyd` -- free energy of hydration of methane (very simple). FEP
  and TI methods.

* `CH4-CF4` -- free energy difference of transforming methane into
  perfluoromethane, in water (simple). BAR method.

* `CC-CO` -- free energy difference of transforming ethane into
  methanol, in water (more complex). FEP, TI and BAR methods.
