Update dtags-activate script

Skip missing directories in run command

Fix bug in argument handling in run command

Improve tab completion scripts and fix a bug in run command

Overhaul for version 4.0.0

Document support for Python 3.7

Add license and tests_require to setup.py

Update README and make it clear that windows is not supported

Update README and bump up version for PyPI

Allow the # character in directory paths and tag names