Merge pull request #583 from ascott1/master

Small screen design improvements & SxS IE fix
replace default appendix img src with background img
use jquery unveil to lazy load images on scroll
build
Merge pull request #584 from ascott1/lazyload

Lazy load images
use lighter bg image for lazyload
better spacing on about page
super small landing page change
Merge pull request #586 from jehlers/master

super small landing page change
merge upstream
Merge pull request #585 from ascott1/sprint-19-design

Small design changes
remove unnecessary appendix templates
remove extra interp markup
remove unecessary c.marked_up
Merge pull request #587 from ascott1/sprint-19-design

Remove unnecessary appendix markup
'easy read' spacing
fix external link behavior
correct about page internal link offsets
internal links need hover states
only offset inner-content on about page