[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.
I disagree, as the lack of a colon keeps the sentence flowing IMO. I don't think the example's are large enough to warrant an interruption (obviously a comma is an interruption, but less so than a colon).