Add test for exports.

Test against underscore functions.

tests/exports.js

@@ -0,0 +1,9 @@
+var _ = require('underscore');
+var deepEqual = require('assert').deepEqual;
+var s = require('../dist/underscore.string');
+
+test('#exports', function() {
+  deepEqual(_.intersection(Object.keys(s.exports()), _.functions(_)), [],
+    "Conflicts exist between exports and underscore functions"
+  );
+});