Issue 6, explanation of choice of JSON for preview

Attempted to explain why JSON was used to represent the CSV when delivering a preview to the browser.
Merge pull request #3 from rossjones/issue-6-csv-preview-as-json

Issue 6, explanation of choice of JSON for preview
modified intelligent preview use case to better include Ross' input

changed the order of the paragraphs to better integrate the additions
from Ross Jones. Also add bidirectional references for the two
associated requirements
added UC-SupportingSemantic-basedRecommendations
Merge branch 'gh-pages' of https://github.com/w3c/csvw into gh-pages
edit UC-SupportingSemantic-basedRecommendations
edit UC-SupportingSemantic-basedRecommendations
fixed motivation reference in cellmicrosyntax requirement