Update database.rst
Update database.rst

Mysql databse url format should like postgresql.
fuzeman/peewee,lez/peewee,jnovinger/peewee,coreos/peewee,zhang625272514/peewee,bopo/peewee,wenxer/peewee,new-xiaji/peewee,stas/peewee,Sunzhifeng/peewee,coreos/peewee,softside/peewee,bopo/peewee,coreos/peewee,jarrahwu/peewee,Sunzhifeng/peewee,py4a/peewee,ghukill/peewee,mackjoner/peewee,jarrahwu/peewee,bopo/peewee,coleifer/peewee,fuzeman/peewee,ronyb29/peewee,zhang625272514/peewee,jnovinger/peewee,coleifer/peewee,new-xiaji/peewee,zhang625272514/peewee,coleifer/peewee,Sunzhifeng/peewee,teserak/peewee,wenxer/peewee,new-xiaji/peewee,jarrahwu/peewee