title: Ionic 2 http.get() issue
body: <p>I tried to make a <code>http.get()</code> call with these two methods.</p>
  
  <p>First:</p>
  
  <pre><code>getResults(){
      return this.http.get('http://localhost/api.php')
      .toPromise()
      .then( data =&gt; data.json() );
  }
  </code></pre>
  
  <p>Error Shown:</p>
  
  <pre><code>3     122412   error    EXCEPTION: Uncaught (in promise): Response with status:0  for URL: null
  4     122413   error    ORIGINAL STACKTRACE:
  5     122413   error    Error: Uncaught (in promise): Response with status: 0  for URL: null
  ..........
  </code></pre>
  
  <p>Second:</p>
  
  <pre><code>getResults(){
      return new Promise((resolve, reject) =&gt; {
        this.http.get('http://localhost/api.php')
          .map(res =&gt; res.json())
          .subscribe(data =&gt; {
            resolve(data);
          }, (err) =&gt; {
            reject(err);
          });
      });
  }
  </code></pre>
  
  <p>Error Shown:</p>
  
  <pre><code>2     925052   error    EXCEPTION: Uncaught (in promise): Response with status:0  for URL: null
  3     925052   error    ORIGINAL STACKTRACE:
  4     925053   error    Error: Uncaught (in promise): Response with status: 0  for URL: null
  .......
  </code></pre>
  
  <p>Which method should I use and what could be the issue?</p>