title: rxjs-compat vs pipe() method
body: <p>I used to chain methods with Observable like </p>
  
  <pre><code>Observable
  .of('bla')
  .map(text =&gt; 1)
  .filter(value =&gt; value === 1)
  .subscribe(value =&gt; console.log(value));
  </code></pre>
  
  <p>But now, I realize that since angular V6, we should use pipe() method like</p>
  
  <pre><code>Observable.of('bla').pipe(
  map(text =&gt; 1),
  filter(value =&gt; value === 1)
  ).subscribe(value =&gt; console.log(value));
  </code></pre>
  
  <p>As I saw lot of code that uses pipe(), I suppose I should use it, but is it really 'mandatory' ? or rxjs-compat will do the trick ?</p>