Allow rethinkdb input plugin to work with RethinkDB 2.3.5+ databases that requires username,password authorization and Handshake protocol v1.0
* remove top level header not required in sample config
* remove top level header not required in sample config
This will basically make the root directory a place for storing the
major telegraf interfaces, which will make telegraf's godoc looks quite
a bit nicer. And make it easier for contributors to lookup the few data
types that they actually care about.
closes#564