title: find range of substring of string
body: <p>I am trying to figure out how to get a range of a substring within a string. By range I mean where the substring begins and where it ends. So if I have following string example:</p>
  
  <pre><code>NSString *testString=@"hello everyone how are you doing today?Thank you!";
  </code></pre>
  
  <p>If the substring I am looking for (in this example) is "how are you doing", then the beginning range should be 15 and the ending range should 31. </p>
  
  <pre><code>  (15, 31)
  </code></pre>
  
  <p>Can anyone tell me how I could do this programatically? Thank you!</p>