title: Calling Twitter API from Postman works, but from Angular 2 app it doesnt'
body: <p>I am trying to use Twitter API in my app.</p>
  
  <p>When I run it from Postman, it works great. </p>
  
  <p><a href="https://i.stack.imgur.com/Hkya0.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Hkya0.jpg" alt="Postman"></a></p>
  
  <p>However, when I run it from my app, using Google Chrome I get </p>
  
  <blockquote>
    <p>XMLHttpRequest cannot load
    <a href="https://api.twitter.com/1.1/search/tweets.json?q=canada" rel="nofollow noreferrer">https://api.twitter.com/1.1/search/tweets.json?q=canada</a>. Response to
    preflight request doesn't pass access control check: No
    'Access-Control-Allow-Origin' header is present on the requested
    resource. Origin '<a href="http://localhost:3000" rel="nofollow noreferrer">http://localhost:3000</a>' is therefore not allowed
    access. The response had HTTP status code 400.</p>
  </blockquote>
  
  <p>Here is my code for it</p>
  
  <pre><code>...
  
       getTweets(hashtag : string){
          var headers = new Headers();
          headers.append('Authorization', 'Bearer AAAAAAAAAAAAAAAAAAAAAONruQAAAAAAfxQda4njz64axXN9sw4U0oU%3Dr1niTwKwXoOZXmZczDKgN0wWHWEMPrPcnXXMgVQhiTIzays7J');
          var requestOptions = new MyRequest();
          requestOptions.headers = headers;
  
        return this.http.get('https://api.twitter.com/1.1/search/tweets.json?q=montreal', requestOptions);  
      }
  }
  
  class MyRequest implements RequestOptionsArgs {
      public headers: Headers;
  }
  </code></pre>