Update version to 3.0.0-snapshot
Update version to 3.0.0-snapshot

It is weird that bandit has version 2.0.0 although this is
by far not true.
Until we release 3.0.0, let's be 3.0.0-snapshot in Git
(without nasty git-describe logic).
After a release of 3.0.0, let's simply release more often
and increment the respective number in every feature branch.

joakimkarlsson/bandit,ogdf/bandit,ogdf/bandit,joakimkarlsson/bandit,joakimkarlsson/bandit