Add max_execution_time
Change default user agent list
Change how to benchmark, and update the result

Environment:
  CentOS 6.5 (64bit) on VirtualBox (Host: MBA OS X Yosemite)
  PHP 5.5.18
    Zend OPcache v7.0.4-dev
    Xdebug v2.2.5
  Apache 2.2.15