Adds dbm move

[claudiubelu]

The module "anydbm" has been moved to "dbm" in Python 3.

Defines the "dbm" move from "anydbm".

[1] https://docs.python.org/2/library/anydbm.html

[benjaminp]

Hi, thanks for the PR. Could you please add this to the table in document/index.rst, please?

[benbariteau]

I think this branch has it backwards. This module moved from anydbm to dbm, not the other way around. https://docs.python.org/2.7/library/anydbm.html#module-anydbm

[benjaminp]

Closing as a duplicate of #299.