Fix .travis.yml for PHP7 and try to fix a DB test
diff --git a/tests/codeigniter/database/DB_driver_test.php b/tests/codeigniter/database/DB_driver_test.php
index c04c42b..26416d3 100644
--- a/tests/codeigniter/database/DB_driver_test.php
+++ b/tests/codeigniter/database/DB_driver_test.php
@@ -6,7 +6,7 @@
 	{
 		$config = Mock_Database_DB::config(DB_DRIVER);
 		sscanf(DB_DRIVER, '%[^/]/', $driver_name);
-		$driver = $this->$driver_name($config[DB_DRIVER]);
+		$driver = $this->{$driver_name}($config[DB_DRIVER]);
 
 		$this->assertTrue($driver->initialize());
 	}