Fix typo in comment.

src/social-likes.js

@@ -576,7 +576,7 @@
 
 	function template(tmpl, context, filter) {
 		return tmpl.replace(/\{([^\}]+)\}/g, function(m, key) {
-			// If key don't exists in the context we should keep template tag as is
+			// If key doesn't exists in the context we should keep template tag as is
 			return key in context ? (filter ? filter(context[key]) : context[key]) : m;
 		});
 	}