Feature/obfsproxy

the new version of leap_cli (in develop branch, unreleased, not in master branch) has two handy things that would be good here:

(1) macros are now stored in leap_platform under provider_base/lib/macros (although support for this is not yet in leap_platform:develop, but i hope to merge it in soon).

(2) there is a new macro called 'pick_node'. it will pick a random node, being smart about evenly allocating all the nodes and remembering which node picked which other node.

you can see example usage here: https://github.com/elijh/leap_platform/blob/feature/couch/provider_base/services/_couchdb_mirror.json