recovered missing branding; softened colors in CSS; completed tour, learn, and develop guides

collapsed participate and read into explore guide, with pages for community, videos, and books

changed group photo

tweaks to font sizing, based on media query for typical projector size

improved media queries for 3 sizes of guide; still issues with ie9

improved responsive layout on ie9

revised connection lost to use show/hide instead of add/remove
Merge pull request #674 from akollegger/guide

Replace splash screen with built-in guide