New in version 0.2

*   Python 3 support
*   Dictionary unification
*   Use multiple dispatch to extend unify, reify, isvar
*   Add convenience class decorator `unifiable` to facilitate trivial 
    unification of user classes
*   Add term operations term, arguments, operator, also multiply dispatched
*   Depend on the toolz library
*   Performance degredation as a result of multiple dispatch
*   Arithmetic goals
*   Improved set matching performance
