Feature/revise spec

DO NOT MERGE. FOR DISCUSSION ONLY. @zdne @honzajavorek Please comment.

This PR updates the SPEC based on @zdne and my multiple discussions and refinements.

It also pulls in the current README with some typo fixes. 

@zdne I basically forked and update your branch for this PR into master. Would you prefer I just fork off of master and just create a branch the only adds the spec? Let me know.
I think the only constraint would be on the block description presumably. But you would have to use a separator before the text block to separate it from a trailing text block. So, I think we should keep the multiline blocks right under the member.