Hi,

thanks for an awesome plugin; it was a relief to find when I introduced pylint to an existing django project and was swarmed with errors from django class Meta and so forth.

My team had an issue with getting the plugin to work in some instances.

Specifically; using a virtualenv/global installation of pylint and plylint django which did not include django. It may seems silly, but I think it's a valid usage pattern.

The django typical lint errors kept being reported, and we were pretty confused as to why. Of course, django had to be installed on path.

I didn't see anywhere in the readme that django had to be installed. It's a minor nuisance to solve, but it'd be nice to help the next person by either:

• letting them know in the readme
• raising an error when pylint_django is loaded if django is not installed
• adding django to requirements in setup.py

I'm in favour of the last option. Glad to create a PR for the option that the maintainer(s) prefer, if any.

Thanks