[RFC] Misc. msgpack-rpc doc fixes

Hi,
I'm not totally sure what this project's guidelines are in regards to docs, but most of these are pretty simple changes so I'm copefully complying by them.
I've signed the CLA, and I believe this should supersede #1352.
It's the tabs. This line at the bottom: ` vim:tw=78:ts=8:noet:ft=help:norl:` sets the tabstop, so I guess its ok.