Avoid loading lodash when not needed in unit tests.

test/backbone.html

@@ -53,7 +53,7 @@
 				global_test_results = results;
 			});
 
-			// load Lo-Dash again to overwrite the existing `_` value
+			// load the build of Lo-Dash
 			document.write('<script src="' + ui.buildPath + '"><\/script>');
 		</script>
 		<script>