removed marketing css/scss files

all styles have been merged into app.css in previous commits
add seminal article template
made external footer links open in new window
.brand-name scales on mobile and displays in camel case
removed sitemap link from footer
Added 18 'seminal articles' pages
Added learn.html modals and content
learn section content
Added 404 and error pages
Merge branch 'new-registration' of https://github.com/bradstrong/practiceUpdate into new-registration
Updated SASS and modal's markup in learn.html. Updated Melanoma article
corrected grammar and spelling on landing pages
corrections to text on generic and oncology landing pages
removed learn modal-feature-disabled from app.js
fixed content and styles of 404 page
landing page corrections. Disclaimer and course links added to CME modals.
urology landing page errors fixed
Merge branch 'new-registration' of https://github.com/bradstrong/practiceUpdate into new-registration
Added appearance of active link. Edit mokups.
updated tagline on landing pages