Changes the `$kinvey.User.search` URL to use `/?` instead of ‘?’

Manual merge of 81080d965abb62329bb7844f4a3e5e6e8bff7fac from master into v2-dev: fixes issue (#22) and references pull request #18.
Replaces the `?` in the user query URL to `/?` which prevents the `AppNotFound` from being returned from Kinvey.