Fix paths for Windows

[mikkeyboi]

The updated swift-build by @compnerd has updated lldb python bindings. Thank you @compnerd for completing the quick feature request. The updated PYTHONPATH now points to path/to/toolchain/usr/lib/site-packages which contains the lldb module.

This PR also fixes the REPL path. After running register.py all the paths appear correct now.

I'll open an issue for this work-in-progress, and if possible I'd like to ask others to try testing this as well. Some TODO:

• Update Documentation for Windows instruction
  • Users will have to follow the TensorFlow/swift repo Windows Instructions, and we will need to update the toolchain that has lldb, unless we add Nightly installation instructions from compnerd/swift-build repo.
• Successful kernel initialization (need testing)
  • After creating a notebook, running the kernel gives me an ImportError: DLL load failed. during _lldb.pyd import ModuleNotFoundError during Kernel Initialization (Windows) #98.
• IDE Support
  • There are some who prefer to use PyCharm/VS Code/Atom/Nteract to run their Jupyter Notebook, although it's likely that this will work once the kernel initializes and REPL is functional.