ENH : overhauled display
ENH : overhauled display

 - use imshow overlay with alpha to show mask
 - properly handle call-back removal
 - removed hard-coded write-to-disk

ericdill/xray-vision,sameera2004/xray-vision,giltis/xray-vision,sameera2004/xray-vision,giltis/xray-vision,licode/xray-vision,ericdill/xray-vision,licode/xray-vision