Add python 3.10 support and drop python 3.6 support

* Add python 3.10 support (add to test matrix)
* Drop python 3.6 support
* Use tomli instead of toml for toml support
* Update dependency range and dev dependencies

Update changelog

Release version 0.9.0

Version 0.8.0

Merge pull request #17 from daviskirk/fix-15

Fix #15

Install pytest explicitely to work around setup bug

Fix rst

Added 0.7.2 release

BUGFIX: Update logging settings recursively

- Add test to guard against regression
- Allow partial logging settings to be set without overriding the rest of the
  default logging configuration

upgrade travis config