ENH: allow binstar user to configure verify

The user must do :

    binstar  config --set verify [True|False|/path/to/rootCA.pem]
    -or-
    binstar  config --set sites.siteName.verify [True|False|/path/to/rootCA.pem]

cc @bkreider @lilmatt 

I still can not get the `/path/to/rootCA.pem` option to work. maybe I am creating my self signed cert wrong.