workflow after separating out Core package

[thorek1]

when updating to the latest SymPyPythonCall unSym (and many other functions) are no longer exported. I am not sure if this is a feature and we are supposed to import the core package as well or a bug :) I would advocate for exporting the functions from the PythonCall and PyCall packages and leave the Core package invisible to the user.

[jverzani]

Thanks. that was bad form. I'll put in proper deprecations in the next release, hopefully today. (For now, unSym is just the unicode \downarrow[tab].)

[jverzani]

CLosed in #36. Please reopen if that didn't address the issue.