update readme

@zdne @pksunkara @smizell I have edited the README and one example file. I am holding of on other example files pending chatting with @zdne. ITMT, I have added a few comments in-line that need clarification per an email I sent @zdne and questions I have.

Also, I have switched the order of presentation here from JSON first to MSON first in the examples. The point of this document is to introduce MSON and the JSON makes more sense once you read the MSON vs. the opposite (my experience reading this the first time). In the context of MSON being used to replace JSON in api-blueprint, maybe the logic is opposite, but if we are going to share this generally with people, then I think the order I have it is correct.
Since we are mentioning Mixin in the README shouldn't it have at least one sentence comment on the inheritance while defining a named type?