Fix link to user pictures

[ThyMYthOS]

E.g. https://boiling-spire-20724.herokuapp.com/media/uploads/2017/07/12/amarok.png does not work.

[mrWinston]

Alrighty,
I just realized, that we cannot use heroku to serve the media files uploaded by the users. So this will take a while to sort out. I guess, there's no way around s3 for serving them. I'll try to set it up ASAP, In the meantime, i'd suggest to ignore the profile picture.