avoid type errors

Merge pull request #21 from schmittjoh/scrutinizer-patch-1

Scrutinizer Auto-Fixes

Merge pull request #12 from stof/patch-2

Fixed the branch alias for master

fixes tests on PHP 5.3

Merge branch 'master' of git://github.com/schmittjoh/php-collection

Merge pull request #2 from matthiasnoback/php_usort_compliant

Made sorting behavior compliant with usort

removes duplicate license