0.3.3

Most important changes: ExtSlice and Index are no longer used.

Support Python 3.9

This way, I can run onyl actuall tests in Fedora.
Also pytest-pep8 does not work with recent pytest versions.

Separate linting toxenv from testing toxenv

Do not forget type_comment field!

Fix #49

Fix handling of ast.Assign

Only minor change: alias nodes get line info.
All existing code should keep working as usual

And use it to test python 3.10

Testing support for python 3.10

This gives a 5 to 10% speedup in ast generation depending on the input. As gast
relies on the tree generated by the ast module and does not create any sharing
with the original tree, we're slower, but that's what make it a clean and simple
module :-)

Fix #58

Allow either 0 or #fields arguments, with #fields honoring keyword arguments

This allows to remove the test dependency on astunparse, while adapting
CPython's astunparse to gast AST

Fix #64