These updates allow to recognize IE11, the new Opera with Blink engine (15+) and Maxthon.
Windows 8.1 is recognized as different OS from Windows 8, with abbreviation W81.
I also created a new UA test script including a number of modern browsers and renamed the previous version to UserAgentParser.test.oldbrowsers.php
@mpopp75 Thanks for the pull request! Please review the test failure and then squash/rebase your commits. It's not necessary to have eight commits for this. Thanks!
Closing this pull request (replaced by https://github.com/piwik/piwik/pull/161)