Release 2.0.0

[sunwire]

Maybe it's time for the new release?

[jmwilson]

I think it's feature-complete for release. There are some "cosmetic" things I would like to make consistent (e.g. the use of "volume" or "current block" in the output and documentation), but haven't gotten around to trying some changes.

[jonasstein]

I suggest to close #95 and #69
before tagging 2.0
It is not a big thing and licenses can not be clarified too early
The distributions need to know about the changed dependencies.

[jonasstein]

2.0.0_rc is ready for testing