[RELEASE] Released version 2.4-dev0

Released version 2.4-dev0 with the following main changes :
    - MINOR: version: it's development again.
    - DOC: mention in INSTALL that it's development again
diff --git a/VERSION b/VERSION
index 276cbf9..36f2630 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.0
+2.4-dev0