Update 404 page

Summary: Prior to this diff the 404 page was not getting the proper
background image because it was using the pageminimal template. It
looked like this:

https://drive.google.com/file/d/0B6vYbVKRyOPDaVBUalFfMVpwQ1E

After it looks like this:

https://drive.google.com/file/d/0B6vYbVKRyOPDMjh2Yk43U2pwTTg

I looked at updating the pageminimal template to include the proper
information but it looks like it is significantly diverged from the
base home template. As such I thought that the best solution to the
issue was just using the home template, but this might not be the
actual right solution.

This diff also gets rid of the "adorable monkey" as meta information
for facebook and twitter since the actual image does not exist inside
of the assets for the site. Again this might not be the correct fix,
but i don't have access to the assets so it seemed ok. It could always
be pulled out of the git history once the asset is included.

Test Plan: Build the site and then open the 404 page. It should not
have the proper background and header. Inspect the meta information on
the 404 page and see that it no longer references the "adorable monkey"
image but rather uses the default one.