title: How to generate OAuth1 HMAC SHA1 signature in swift 3
body: <p>I'm working on a small swift program to work with Yelp API over OAuth-1. I am looking to generate a HMAC-SHA1 signature.</p>
  
  <p>I have the customer key, secret key , token and token secret.</p>
  
  <p>From what I know, to make an API request with <code>OAuth1</code>, we need the following attributes :</p>
  
  <ol>
  <li>1.oauth_consumer_key</li>
  <li>oauth_token</li>
  <li>oauth_signature_method = (HMAC-SHA1)</li>
  <li>oauth_signature</li>
  <li>oauth_timestamp</li>
  <li>oauth_nonce</li>
  </ol>
  
  <p>I have the first <code>1,2,3</code> parts but I don't know how do I generate <code>#4,5,6</code>
  I am kind of new to ios/swift3 so please point me into right direction</p>