Adding Python 3.5 and 3.6 Support

Adding Python 3.5 and 3.6 Support.

Thanks, @bcail.

Django 2.2+ and Python 3.7+ Only

Updating code and requirements to be compatible with only Django 2.2+ (including 3.0) and Python 3.7 only.

Template Tag Logic Update

Fixes template debug log issue.

IP Address Header Setting

New setting to enable setting which header to grab the IP address from when capturing it with terms acceptance. Added info to README.

Querystring Passthrough for Redirects to Terms

Integrates #75 .

Django 2.1 Compatibility

Added support for Django 2.1.

Template Tags for Terms

@adibo contribution for templated terms.

International tags

@LittleLampLight added international tags to the templates.

Exclude User With Specific Permission

New feature to enable excluding users with a specific custom permission. Thanks to @ciarancourtney !

Django 2.0 Support

Thanks to @arthru for help with the Django 2.0 support!