update requirements
don't use nose.collector for test discovery
update fox test setup
reworked ZODBGraph to work with rdflib4 (based on IOMemory store)
allow tests to close and reopen db
use transaction commit to actually test storing of data
time read and delete as well
use tox to run travis tests
added .gitignore
rename ZODBGraph to ZODBStore
require rdflib >= 4.1