Fix Warning: file_get_contents(http://wayback.archive.org/web/*/powderlines.ch) [<a href='function.file-get-contents'>function.file-get-contents</a>]: failed to open stream: HTTP request failed! HTTP/1.1 404 Not Found in (path_to_piwik)/core/Http.php on line 417 

Fixes #3670

git-svn-id: http://dev.piwik.org/svn/trunk@7757 59fd770c-687e-43c8-a1e3-f5a4ff64c105