bin/riemann-riak: Add two more keys to core_services

Add `node_gets_set` and `node_puts_set` to core_services, to catch Set
get/put stats.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
riemann-riak: Add support for node_get_fsm_objsize_*

This changes how the fsm stats work, so we can add support for
`node_get_fsm_objsize_*` too, with as little code change as possible.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #89 from algernon/f/riak-extra-stats

Add support for some extra Riak stats