function search(){
    if(dirArray.length === 0) return cb();
    dir = dirArray.join('\\');
    var file = dir + '\\.npm-version';
    fs.readFile(file, function(er, version){
      if(er){
        dirArray.pop();
        return search();
      }
      cb(null, version.toString().trim(), file);
    });
  }
Gets the local npm version
@param {function} cb callback accepting (err, version)