Unique indexes (#1971)

* Add unique indexing

* Add unique indexing for username/email

* WIP

* Finish unique indexes

* Notes on how to upgrade to 2.3.0 safely

* index on unique-indexes: c454180 Revert "Log objects rather than JSON stringified objects (#1922)"

* reconfigure username/email tests

* Start dealing with test shittyness

* Remove tests for files that we are removing

* most tests passing

* fix failing test

* Make specific server config for tests async

* Fix more tests

* fix more tests

* Fix another test

* fix more tests

* Fix email validation

* move some stuff around

* Destroy server to ensure all connections are gone

* Fix broken cloud code

* Save callback to variable

* no need to delete non existant cloud

* undo

* Fix all tests where connections are left open after server closes.

* Fix issues caused by missing gridstore adapter

* Update guide for 2.3.0 and fix final tests

* use strict

* don't use features that won't work in node 4

* Fix syntax error

* Fix typos

* Add duplicate finding command

* Update 2.3.0.md

spec/ParseRelation.spec.js

@@ -696,6 +696,7 @@ describe('Parse.Relation testing', () => {
         admins.first({ useMasterKey: true })
         .then(user => {
           if (user) {
+            response.success(user);
             done();
           } else {
             fail('Should have found admin user, found nothing instead');