lib/index.js
function getOutputDir(output) {
  var arr = output.split(path.sep);
  arr.pop();
  return arr.join(path.sep);
}
function getOutputDir(output) {
  var arr = output.split(path.sep);
  arr.pop();
  return arr.join(path.sep);
}
function getOutputDir ( output ) { var arr = output . split ( path . sep ) ; arr . pop ( ) ; return arr . join ( path . sep ) ; }
get output directory from original output
@param  {string} output
@return {string} outputDir
@private
get output directory from original output