Update AUTHORS (#6986)

@hixie told me to add me to the list, see https://github.com/flutter/flutter/pull/6833#issuecomment-260418501
diff --git a/AUTHORS b/AUTHORS
index 377a6a4..e050455 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -9,3 +9,4 @@
 Wyatt Arent <hello@wyatt.ninja>
 Michael Perrotte <mikemimik@gmail.com>
 Günter Zöchbauer <guenter@gzoechbauer.com>
+Raju Bitter <rajubitter@gmail.com>