MySQLDB falls back on pymysql

[mistercrunch]

@LilithWittmann , I decided to privilege MySQLDB over pymysql since it's written in C and probably is more optimized and less disruptive overall to keep it as deps in extras_require don't get applied unless specified.

I still left pymysql in setup.py though for py3 compatibility, people can install MySQLDB if they prefer it for some reason.

Original PR: #424

[LilithWittmann]

OK sounds like a good idea!

[mistercrunch]

I'm having problems with SqlAlchemy when setting my connection URI to mysql+pymysql://, I'll have to dig deeper before I can merge this.

[mistercrunch]

The master branch now uses mysqlclient, which is py3 compatible and a drop in replacement for mysql-python

[mrwillis]

Hi, sorry this is old but I can't see on master that this is changed: link.

Is there any plans to support mysqlclient or another python3 friendly driver?

Thanks!