comment about internalApiVersion protocol

src/main.js

@@ -1,6 +1,9 @@
 
 var FC = $.fullCalendar = {
 	version: "<%= version %>",
+	// When introducing internal API incompatibilities (where fullcalendar plugins would break),
+	// the minor version of the calendar should be upped (ex: 2.7.2 -> 2.8.0)
+	// and the below integer should be incremented.
 	internalApiVersion: 8
 };
 var fcViews = FC.views = {};