Transfer ownership to tenacity

[groodt]

Thanks for this useful package and work over the years.

Given that your priorities now lie elsewhere, would you be open to transferring ownership of the PyPI package name to tenacity?

jd/tenacity#356

No work on your part and a compatibility shim will be added.

[groodt]

Project is maintained here
https://github.com/groodt/retrying/tags

Transfer was here
pypi/support#2205