remove sympy
add traverse.py
curry core
curry traverse
curry branch/core.py
add toolz as dependency
some Py3 imports
sall uses logpy.term rather than term
Python 3 compatibility

func_name
StringIO
ifilter
strategies are no longer variadic
branching strategies are no longer variadic
clean up imports and spacing in core.py
remove util.py
fix doctest in tree docstring
Merge pull request #1 from mrocklin/curry

Refactor