Meddleware for private instances

[phaer]

Hi,

In spite of the coming pump.io integration and a more fine-grained permission system, I wrote a simple meddleware which prohibits access for all non-authenticated users a few weeks ago.

I do not know the policy, but as meddlewares are optional I thought maybe you want to add it to the main repo, or should i add it to ​http://wiki.mediagoblin.org/Available_Plugins ?

Source is at ​https://github.com/phaer/mediagoblin/tree/phaer/private-meddleware