bumped version to 2.5.1-DEV

CHANGELOG

@@ -1,3 +1,7 @@
+* 2.5.1 (2018-XX-XX)
+
+ * n/a
+
 * 2.5.0 (2018-07-13)
 
  * deprecated using the spaceless tag at the root level of a child template (noop anyway)

lib/Twig/Environment.php

@@ -16,12 +16,12 @@
  */
 class Twig_Environment
 {
-    const VERSION = '2.5.0';
-    const VERSION_ID = 20500;
+    const VERSION = '2.5.1-DEV';
+    const VERSION_ID = 20501;
     const MAJOR_VERSION = 2;
     const MINOR_VERSION = 5;
-    const RELEASE_VERSION = 0;
-    const EXTRA_VERSION = '';
+    const RELEASE_VERSION = 1;
+    const EXTRA_VERSION = 'DEV';
 
     private $charset;
     private $loader;