Initial release of akamai-open/edgegrid-auth

• Initial release as a separate package
• PHP 5.3 compatibility fixes

Note: If you are using akamai-open/edgegrid-client as a composer dependency, it will continue to function without any changes. If you are using git, svn, or have been downloading releases, you will now find them at akamai-open/AkamaiOPEN-edgegrid-php-client