Fix CommonJS relative require generation, and test it

js/binary/proto_test.js

diff --git a/js/binary/proto_test.js b/js/binary/proto_test.js
index 817f8a7..3b4aa17 100644
--- a/js/binary/proto_test.js
+++ b/js/binary/proto_test.js
@@ -32,7 +32,7 @@
 
 goog.require('goog.testing.asserts');
 
-// CommonJS-LoadFromFile: testbinary_pb proto.jspb.test
+// CommonJS-LoadFromFile: ../testbinary_pb proto.jspb.test
 goog.require('proto.jspb.test.ExtendsWithMessage');
 goog.require('proto.jspb.test.ForeignEnum');
 goog.require('proto.jspb.test.ForeignMessage');