fix gunicorn usage in readme
fix gunicorn usage in readme

Instructions from @justinvw. Fixes gh-2.

larsmans/AVResearcherXL,beeldengeluid/AVResearcherXL,beeldengeluid/AVResearcherXL,larsmans/AVResearcherXL,beeldengeluid/AVResearcherXL,larsmans/AVResearcherXL