Add a rule to redirect non-admin users

This is another solution to the issue of the node/add page being visible to non-admin users ( https://github.com/NYC-Camp/website/pull/60 ). I think this solution works well and it is an easy solution to work with and add additional paths to, should the need arise. 

Once the dust settles on what we're going to do with COD, we can perhaps fold this module's functionality into one of the larger COD modules, like COD Sessions, for example

Please review @jonpugh and @likewhoa