Adjust pizza logo height and h1 font size.

* Change the pizza logo height to be a height instead of min-height, this fixes
  the stuttering on Firefox
* Bump the h1 font-size down so it does not break to two lines on Firefox

Fixes #12.
Merge pull request #13 from brettchalupa/firefox-pizza-fix

Adjust pizza logo height and h1 font size.