fixed uniqueid so that it is a function as expected by index.js and elsewhere

also added test for uniqueid. only test that two calls to uniqueid return unique enties. had to modify the output slightly and added a counter to the system otherwise two back to back calls would return the same value.

lib/uniqueid.js

@@ -1 +1,8 @@
-module.exports = "pjax" + (new Date().getTime())
+module.exports = (function() {
+  var counter = 0
+  return function() {
+    var id = ("pjax" + (new Date().getTime())) + "_" + counter
+    counter++
+    return id
+  }
+})()