on mobile can't get more than first touch

[jeezs]

in order to capture more than the first touch, the 'touch def' should accept optional params :

def touch_x(touch_nb = 0)
#@native.originalEvent.touches[#{touch_nb}].pageX
end

def touch_y(touch_nb = 0)
#@native.originalEvent.touches[#{touch_nb}].pageY
end

[elia]

@jeezs the proposed implementation looks good, can you please submit a pull-request with that change?