title: Error installing packages from github
body: <p>I can't install packages from github:</p>
  
  <pre><code>&gt; install_github('cranvas', 'ggobi', args="--no-multiarch")
  Installing github repo(s) cranvas/master from ggobi
  Installing cranvas.zip from https://github.com/ggobi/cranvas/archive/master.zip
  Error in function (type, msg, asError = TRUE)  : couldn't connect to host
  </code></pre>
  
  <p>this is my session:</p>
  
  <pre><code>R version 3.0.1 (2013-05-16)
  Platform: x86_64-pc-linux-gnu (64-bit)
  </code></pre>
  
  <p>NB: <code>install.packages</code> works as usual, it's just with github the issue. Have some of you ever faced this? Thanks</p>