Fixes #333 - breaks up the image article into preferred format of articles
Fixes #334 - broke up the video article into smaller chuncks
Updated track element screenshot to match live sample
Update size-videos-correctly.markdown

Small nit-- adding full-stop to description.
Update quick-reference.markdown

Small nits-- adding full-stops to intro and description.
Merge branch 'develop'

* develop:
  update from grunt build
  Final improvements on the header
  updated spotlight header
  Update to spotlight, improved related guide module - added an extra resource item
  updated some colors and fixed overflow issue on spotlight header
  Minor tweak for default naming in nav
  Updated section name in nav for narrow screens
  Improvement to header and main navifation
  Rework on the nav for mobile
  Merging in pre-fix changes
  Fixing an issue with content breaking on /getting-started/your-first-multi-screen-site/responsive.html - the code include should not be indented in the markdown, as markdown double-wraps it by treating it as code. #inception
  Update to footer
  refactored google header
  Updating related guides
  updated some modules in styleguide
  updated fonts from grunt
  Fixing 190
  updated fonts from grunt
update from grunt build
Update content.markdown

Slight rewrite of sentence introducing headline.
Updating content to have the new related articles
Merge branch 'master' of github.com:google/WebFundamentals
Reenable icons in devsite build
Merge branch 'master' of https://github.com/google/WebFundamentals
Merged develop into master
Updated filed from grunt build