DEV: Bump version to 0.9.0

REL: Bump version to 0.8.0 [skip ci]

REL: bump version to 0.7.1

DEV: bump version to 0.7.0

DEV: bump version to 0.6.0

raise version to 0.5.0

change REQUIRED vak to 0.3.1, bump version to 0.4.4 in setup.py

change REQUIRED and bump version in setup.py

- add qualifier of `>=0.3.0' for vak in REQUIRED (and in 'article')
- bump tweetynet verison to 0.4.3

bump version to 0.4.2 in __about__ and CHANGELOG

bump version to 0.4.1 in setup.py