CHanges in `Connection()` (medium-sized) and `Stream()` (extra small)
Style check (flake8)
Refactoring in Connection() and streams.*,
changes in streams.Aspects() - read docstring, new tests
Fixed bug in diaspy.models.Post.__str__, added logout() method to
Connection()
One can now remove() aspects by their name, repr(Post) now returns more
detailed string, new tests
Unnecessarily complex code removed from Aspects().getID()
Last commit before merging into master:
`diaspy.streams.Activity` now inherits from `Stream` and not `Generic`
`diaspy.streams.Aspects` got some refactoring,
new tests added,
testconf file must be updated in order for new tests to run (documented in `testconf.md`),