Install php-ast in Travis

Author: Philo Hamel

.travis/before-script.sh

@@ -20,6 +20,7 @@ elif [ "${PHP_MD}" = '1' ]; then
 elif [ "${PHP_STAN}" = '1' ]; then
     exit 0;
 elif [ "${PHP_PHAN}" = '1' ]; then
+	pecl install ast;
     exit 0;
 fi