py-ansi: updated to 0.3.7

0.3.7

Enable concatenating a string and a sequence, not just a sequence and a string.
Enable empty sequences that evaluate to the empty string.
Allow importing the main module to import all submodules
Fix ECMA-48 link in README.md
Add license to setup.cfg
bugfix sequence in `ansi.cursor.erase('')`
Add `bg=True` argument for `ansi.colour.rgb.rgb256()`

(adam)