Looping the metrics back through the same channel could result in a
deadlock, by using a new channel and locking the processor we can ensure
that all stages can make continual progress.

It is not possible to encode a measurement, tag, or field whose last
character is a backslash due to it being an unescapable character.
Because the tight coupling between line protocol and the internal metric
model, prevent metrics like this from being created.

Measurements with a trailing slash are not allowed and the point will be
dropped.  Tags and fields with a trailing a slash will be dropped from
the point.

Line protocol does not require or allow escaping of backslash, the only
requirement for a byte to be escaped is if it is an escapable char and
preceeded immediately by a slash.

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