Add paper-button dependency

Change-Id: Ic23f3afa5eb9f9aefabf1bc041c33ce3fa92739f
diff --git a/WORKSPACE b/WORKSPACE
index 9bfd28f..ac4d04b 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -1083,6 +1083,13 @@
 )
 
 bower_archive(
+    name = "paper-button",
+    package = "polymerelements/paper-button",
+    sha1 = "41a8fec68d93dad223ad2076d68515334b2c8d7b",
+    version = "1.0.11",
+)
+
+bower_archive(
     name = "paper-input",
     package = "polymerelements/paper-input",
     sha1 = "6c934805e80ab201e143406edc73ea0ef35abf80",