#6 Adding basic markup for Highlights section

Basic markup makes a 3x3 grid until the window is less than 800px where
it will collapse down to a single column view. Design is rough — we
need to crop images to have consistent aspect ratio and get a few new
images (the current ones are too text heavy).
#6 Cropping images to 2:1 aspect ratio

Cropping images to give them a uniform height so the grid looks nice. I
cropped at 2:1 to accommodate the images with text already on them. I
think we should consider not having text on the images (aside from the
logo) and letting the headlines speak for themselves (we could also
move the headlines over the image at that point).
#6 Small CSS tweaks

a) Adjusting padding on each highlight’s text content
b) On mobile devices, each highlight will take up the entire width of
the device up to 600px.
Small idea for jose's letter

Fix inline styles later
Merge pull request #24 from dan-massey/master

Merge master into gh-pages