Remove text-shadow from main nav to make characters less blurry.

It appears that someone attempted to remove the text shadow by setting the offset and size to 0px, but this still results in blurry text, at least in some browsers (Chrome on Mac). Setting it to none instead removes the shadow entirely.
Merge pull request #1 from blowery/patch-1

Remove text-shadow from main nav to make characters less blurry.