Minor Style tweaks

Improved crispness and readability of a few links and buttons. Namely, 'info' buttons (I only noticed any on the 'About' page), visited links, and links in the main navbar.  I tried to make the shadows non-obvious since Pullup is using a flat style, but I felt they made the text appear crisper and much easier to read.  The visited links I just darkened a bit to make them easier to read against the white background.