title: rx kotlin subscription not working, not receiving items
body: <p>I created a function which returns an <code>Observable&lt;String&gt;</code> with file names, but I don't get any event in my subscription where I call this method. Also there is no call of onError, or onComplete <br>
  See my code:</p>
  
  <pre><code>fun getAllFiles(): Observable&lt;String&gt; {
  
      val allFiles = File("/Users/stephan/Projects/Playground/kotlinfiles/")
              .listFiles { file -&gt; !file.isDirectory() }
      return observable { subscriber -&gt;
          allFiles.toObservable()
                  .map { f -&gt; "${f.name}" }
                  .doOnNext { println("Found file $it") }
                  .subscribe { subscriber}
      }
  }
  
  fun test() {
      getAllFiles()
              .doOnNext { println("File name$it") }
              .subscribe(
                      {n -&gt; println("File: $n")},
                      {e -&gt; println("Damn: $e")},
                      {println("Completed")})
  }
  </code></pre>
  
  <p>Though everything is being called in the <code>getAllFiles()</code> function, so what am I missing?</p>