Test enhancement

[peter279k]

Changed log

• Drop the php-5.3, php-5.4 and php-5.5 because they are old PHP versions.
• Set that package is at least version isphp-5.6
• Remove the --dev option because it's deprecated and it's the default option.
• Use the psr-4 autoloader rather than using the psr-0 autoloader.
• Add the autoload-dev in composer.json to load the related test classes.
• Use the class-based PHPUnit namespace to replace the original namespace.
• Set the different PHPUnit version for different PHP versions tests.
• Use the native preg_match_all function to filter the non-numeric strings.
• If possible, it should release the new version.