Postfix-mta-sts-resolver

Minor bugfix and refactoring; introduces 100% test coverage

This release contains important fix of query parsing issue which could be causing to incorrect daemon responses.

This release splits main package dependencies into optional extras in order to reduce efforts of distro packages maintainers.

Changes:
* Installation procedure changed. Now full-featured package is pulled with `pip3 install postfix-mta-sts-resolver[sqlite,redis]` command
* Changed default config location to untangle it from postfix config directory. New location is `/etc/mta-sts-daemon.yml`

* Manifest application requests with User-Agent header

Switched to aiosqlite 0.10.0 which more precisely fits connection pooling demands

Fixes Python3.5 compatibility