Overhaul homepage

[agjohnson]

This is a big update, unraveling quite a bit of history trying to revamp the content and graphic elements. It replaces the homepage above the fold graphics with easier to maintain graphics in place of third party custom graphics. The only custom graphic is the main hero graphic, used to fill the space a bit more and to tie things together.

Graphic changes are:

• The main hero image was replaced. It was an unfinished stock art screengrab.
• The 3 feature section graphics were replaced with colored FA duotone graphics.

Overall, this provides a more polished feel, matches the graphics in the rest of the site without generating more custom glyphs, and added color and detail is nicer than the previous graphics.

Structure changes are:

• Modal for sign up selection, triggered by the hero CTA
• 6 grid feature overview on the front page to add more content
• Blog articles section was dropped to the bottom of the page and replaced with "Resources" instead.

Content changes dictated a lot of these updates.

Closes #127 Closes #42 Closes #53 Closes #41 Closes #32 Closes #122 Refs #128

[agjohnson]

Note: this is for historical purposes, so this information isn't just hidden in a commit message. I'm looking to merge this and start up on feedback and iteration on these pages, rather than review what is a very difficult amount of work.

[agjohnson]

I can't get the RTD build to work, seems there is a bug with build commands and env vars.

[ericholscher]

@agjohnson Exciting! Should site-community be mostly buildable now?