add a couple specs to autolinker to test number only URLs
add a couple specs to autolinker to test number only URLs

gregjacobs/Autolinker.js,closeio/Autolinker.js,closeio/Autolinker.js,gregjacobs/Autolinker.js,gregjacobs/Autolinker.js,gregjacobs/Autolinker.js,closeio/Autolinker.js,closeio/Autolinker.js