website: remove floating topbar
website: remove floating topbar

This caused more problems than it was worth.

Fixes issue 4301.
Fixes issue 4317.

R=golang-dev, minux.ma, rsc
CC=golang-dev
http://codereview.appspot.com/6818076

pombredanne/go-deleteme,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,dsriram/golang,tv42/old-go,gnanderson/go,tv42/old-go,gnanderson/go,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,apparentlymart/golang,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,apparentlymart/golang,tv42/old-go,apparentlymart/golang,tv42/old-go,gnanderson/go,gnanderson/go,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,apparentlymart/golang,apparentlymart/golang,dsriram/golang,apparentlymart/golang