Don't set server header if it's already set (fixes bug 130)
Don't set server header if it's already set (fixes bug 130)

23Skidoo/snap-server,snapframework/snap-server,snapframework/snap-server,sopvop/snap-server,snapframework/snap-server,sopvop/snap-server,23Skidoo/snap-server,23Skidoo/snap-server,k-bx/snap-server,k-bx/snap-server