title: httr github-API callback URL issues
body: <p>I am using the <code>httr</code> v0.2 package to use the github api as well now. But I am struggling to get past the <code>oauth2.0(...)</code> part in which I get to the browser page for my app, click on 'Allow' and then get redirected to the callback URL page. </p>
  
  <p>The httr github demo suggests using the callback URL as <code>http://localhost:1410</code> but when I get redirected to that page, google chrome suggests that it could not connect to the page and the page it is getting re-directed to is <code>http://localhost:1410/?error=redirect_uri_mismatch&amp;state=DZNFcm8tnq</code>...so I tried a bunch of other ports and overall URLS to no success...</p>
  
  <p>What would be another callback URL and URL that would work?</p>
  
  <p>below is the code I used</p>
  
  <pre><code>require(httr)
  ## Loading required package: httr
  github.app &lt;- oauth_app("github","xxxxx", "xxxxxxxxxxxxxxx")
  github.urls &lt;- oauth_endpoint(NULL, "authorize", "access_token",base_url = "https://github.com/login/oauth")
  github.token &lt;- oauth2.0_token(github.urls,github.app)
  ## Loading required package: Rook
  ## Loading required package: tools
  ## Loading required package: brew
  ## starting httpd help server ... done
  ## Waiting for authentication in browser...
  </code></pre>
  
  <p>which is when I get directed to a page that has the 'Allow' button whichIi click after which I get redirected to the page in google chrome that cannot connect to localhost :1410</p>