Version update for Transcrypt: 3.9.4

[JennaSys]

I know this update has been a long time coming, but I finally had a chance to give the project some care. The dev_3.9.4 branch has now been merged to master branch, and the changelog has been posted.

This update has several changes and feature adds to lists, strings, and dictionaries. Slicing operations in particular were significantly refactored to be more consistent with CPython. As with the prior release, if you were previously relying on a Transcrypt'd behavior for these functions that was not aligned with CPython, they may not work the same way now.

All of the transcrypt autotests are currently passing, but if you run into any new problems with it, please let me know. If I don't hear of any major issues, I should get it pushed out to PyPI in the next week or so once I've had a chance to do some more testing myself.

UPDATE: Transcrypt version 3.9.4 has been deployed to PyPI.