Removing TODO (to be tracked in Bandit wiki)

This change removes the TODO file from the Bandit source tree.  We'll keep
track of these on the Bandit wiki page for now, and - assuming the project
continues to grow - eventually move to the OpenStack tracker:

https://wiki.openstack.org/wiki/Security/Projects/Bandit#TODO

Change-Id: I17da99d2d93237472c05b9e7f8537b90eb53c553