This statement wasn't true anymore
request cache doesn't use the callback anymore
community.py doesn't use the callback anymore
dispersytestclass.py doesn't use the callback anymore
node.py doesn't use the callback anymore
Update doctrings
Add a clear() method to the request cache so we can leave a completely
clean reactor when we stop a dispersy instance.
fix/simplify Community._download_master_member_identity() to not leave
pending tasks behind.
Test that the reactor is clean before and after each individual test execution.
Fully migrate dispersy.py away from the callback.
Migrate main.py to twisted
Port tracker.py to Twisted
Remove callback.py and its tests, not used anymore.
move add identity logic out of Member.has_identity()
move SQL out of DummyMember constructor
create init_community() for community init logic