Make the Expunge.io logo more prominent

[smarziano]

From the Mikva Challenge JJC design session, we heard from the youth that they wanted to see their logo more prominently on the page. There were a couple of recommendations made:

1. Splash page with the logo that would disappear after a few seconds
2. A larger logo in the navbar

As a group, we decided either of these options would be good, but to make sure that it works better on mobile, we would want to make the logo larger in the navbar, and then when the user scrolls, the logo/nav bar shrinks.