Adding Packagist statistics for repo via Poser badges

Related to https://github.com/Behat/Mink/issues/421
Cookies were removed only from current path

1. cookie was removed only from current path
2. session reset caused browser history reset as well
3. support for web fixtures in sub-folders
Merge pull request #38 from aik099/cookie-removal-all-paths-fix

Cookie was only deleted from current path
Merge pull request #40 from aik099/packagist-badges-feat

Adding Packagist statistics for repo via Poser badges