Let pip install pymysql3 for Python 3 and mysql-python for Python 2.
Reverted 71b71f8cf5f77897bce890dd7356e162b6ef282e and installed pymysql3 for Python 3 and mysql-python Python 2.

Conflicts:
	.travis.yml
Merge branch 'python3' of github.com:deschler/django-modeltranslation into python3

Conflicts:
	modeltranslation/translator.py