Remove trailing comma for this._availableLoaders
Remove trailing comma for this._availableLoaders

IE8 (and below) will parse trailing commas in array and object literals incorrectly.
tehvgg/PreloadJS,CreateJS/PreloadJS,CreateJS/PreloadJS,Teino1978-Corp/Teino1978-Corp-PreloadJS,tehvgg/PreloadJS,Teino1978-Corp/Teino1978-Corp-PreloadJS,dmnsgn/PreloadJS,SpringRoll/PreloadJS,SpringRoll/PreloadJS