title: How to convert RxSwift's Single to Observable and ignore `complete` event?
body: <p>The case is following. 
  I have a Single that I receive from a third-party API.
  I want to transform this single to Observable, but the issue is Single transformed to Observable still completes my observable chain after emitting a value which I don't want to happen. I want that my observable never completes.</p>
  
  <p>The question is is there any way easier than 'single.flatMap{ Observable.just($0)}' to do what I want?</p>