Add Python type-checking (pytype etc) support

Currently, I am unaware of any support for static python type checkers ([pytype](https://github.com/google/pytype) / [mypy](http://mypy-lang.org) for example) in any python editor / python-repl-supporting app on the App Store. I tried to build pytype, but ran into problems compiling and linking in the required C code. If this were available, a-shell could potentially be configured to do static type checking for other python editors with a shortcut for instance.