Update README.md

Updated intro section to reflect latest Launch Announcement
Update README.md

added roadmap section
Update README.md
Merge pull request #196 from mebates/gh-pages

Update README.md
Improvements to responsiveness
Add Google Tag Manager tracking code
Merge pull request #197 from ohsk/gh-pages

Update Illustration page with new guidelines
Merge pull request #201 from Scotchester/gh-pages

Improve responsiveness (nav, especially)
Update Shading & Highlights example image