New chrome detection function

If you only match the keyword Chrome your detector will match Chrome, Maxthon, Flock, IE 10.0, IE 9.0, IE 8.0, Iron and RockMelt. New code only match google chrome.
Show'Install Chrome Extension' link only in Chrome
Merge pull request #25 from Kolahzary/patch-8

Patch 8 from Kolahzary - show the 'install chrome extension' only to chrome users - thanks!