Staging

[mitchas]

Merge keyboard navigation branch - issue #228 - into dev.

[kathymd]

I tried navigating through the buttons and About section material, filtering and mapping and graphing points and downloading data - it works great! I also really like the new selected button style in the About section. Only two things I noticed:

• If I refresh the screen, I can't seem to get to the 3 buttons on the landing page - the highlighted box jumps straight from the About icon to DOI Privacy Policy without landing on the white rectangle that contains the text and buttons
• The main nav buttons are a little smaller than they used to be. Not a big deal, but I liked how the filters and everything lined up before when they were slightly larger. Could we change back the size?

[kathymd]

@mitchas you'll need to re-open a pull request when your changes are updated because I delete then replaced the staging branch to keep it in the dev workflow