pad.js: wait write callback instead of buffer callback
pad.js: wait write callback instead of buffer callback

storytouch/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,joequant/etherpad-lite,ether/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite