nanopub v0.2.9

Some of the main issues addressed in this (pre-) release:
Agree a fix for the (wrong) URI returned when publishing to test server #46
Issue with intro nanopub #44
Remove uri argument from Nanopub.from_assertion #38
Fix rdflib bindings for this-is-me nanopub #41
Enforce profile creation with orcid id #39
Improve claim() method #19
Add some sort of retract() method #8
Decide what Format should be - only trig at present #28