title: R TwitteR package authorization error
body: <p>I am following the latest update on <a href="https://github.com/geoffjentry/twitteR">twitteR homepage</a>, and I can't pass the authorization process.</p>
  
  <pre><code>library(devtools)
  install_github("twitteR", username="geoffjentry")
  
  library(twitteR)
  api_key &lt;-  "XXXXXXXXXXXXXXXXX"
  api_secret &lt;- "XXXXXXXXXXXXXXXXX"
  access_token &lt;- "XXXXXXXXXXXXXXXXX"
  access_secret &lt;- "XXXXXXXXXXXXXXXXX"
  setup_twitter_oauth(api_key, api_secret, access_token, access_secret)
  </code></pre>
  
  <p>This is the output I am getting back:</p>
  
  <pre><code>[1] "Using direct authentication"
  Error in check_twitter_oauth() : OAuth authentication error:
  This most likely means that you have incorrectly called setup_twitter_oauth()'
  </code></pre>
  
  <p>I have also tried <code>setup_twitter_oauth(api_key, api_secret)</code>, and this is the error message:</p>
  
  <pre><code>[1] "Using browser based authentication"
  Error in init_oauth1.0(endpoint, app, permission = params$permission) : 
  client error: (401) Unauthorized
  </code></pre>
  
  <p>I don't think there are any other options in <a href="https://github.com/geoffjentry/twitteR/blob/master/man/setup_twitter_oauth.Rd"><code>setup_twitter_oauth</code></a>. Does anyone else encounter this error?</p>