Add `tangled python` command

It's like the `tangled shell` command from tangled.web but without the
tangled.web specific shell locals.
Don't offer to push tag during release

I think all pushing should happen outside the release tool.
Add -y to release command
Prepare release 0.1a4
Back to development: 0.1a5.dev0
Allow .py files to have a .py.template ext in scaffolds

This is necessary so that .py files that have invalid syntax due to
using `${name}` outside of a string won't cause `SyntaxError`s on
installation.
Prepare release 0.1a5
Back to development: 0.1a6.dev0
Update trove classifiers