Behat/Mink — pull request #543 by stof (2014-05-11 07:29:12+00:00)
Title: Fixed the file upload tests on windows

Some drivers (at least Selenium2) are expecting the path to the file to use the right directory separator, unlike PHP which accepts / on all platforms.
Applying realpath on the path will normalize this on Windows.

This allows the driver tests to pass on Windows.