Twig 2.0+ and PHP 7.1+
Add support for Twig 2.0+ (#6) * #99 fixing MacroCompiler, when context did not contain current arguments * updating plovr location * update travis and bumped php version from 5.3 to 5.4 * updated twig/twig@2 * update travis to 7.0, 7.1 * Update to the latest version of PHPUnit.