Add test for rename

test/test-rename-collection.js

@@ -0,0 +1,17 @@
+var test = require('./tape')
+var mongojs = require('../index')
+var db = mongojs('test', ['test123', 'test321'])
+
+test('renameCollection', function (t) {
+  db.test123.drop(function () {
+    db.test321.drop(function () {
+      db.createCollection('test123', function (err) {
+        t.error(err)
+        db.test123.rename('test321', function (err) {
+          t.error(err)
+          t.end()
+        })
+      })
+    })
+  })
+})