Potential fix to issue #1

The nav pulldown is now very good at being resolution-agnostic. This comes with one annoying caveat: the behavior when scrolling down past the nav pulldown while it's open may be confusing to some users. Also, the open-nav hamburger button now moves the focus to the top of the screen. This behavior can't be avoided if the nav is allowed to be scrolled.

Tomorrow I plan to try another potential fix (using a <select> tag for small-resolution navigation) and see which I prefer.
Some stylistic improvements to new nav
More style tweaks to nav

Also improved naming of classes in nav.
Merge branch 'iss1' - Closes issue #1

The nav menu has been improved, particularly for very small resolutions. It has been tested and optimized for all common small resolutions and will at least be functional at uncommon ones (such as for widths < 320px).