Adds Spencer Ellinor to AUTHORS

Author: ask

AUTHORS

@@ -73,6 +73,7 @@ Scott Rubin <srubin@broadway.com>
 Sean Creeley <sean.creeley@gmail.com>
 Serj Zavadsky <fevral13@gmail.com>
 Simon Charette <charette.s@gmail.com>
+Spencer Ellinor <spencer.ellinor@gmail.com>
 Theo Spears <github@theos.me.uk>
 Timo Sugliani
 Vincent Driessen <vincent@datafox.nl>