title: Can't change fonts in ggplot/geom_text
body: <p>I can't set my fonts in geom_text. Here is what I tried:</p>
  
  <pre><code>    labels_test&lt;-data.frame(a=c("a","b","c"),b=c(1:3),c=c(3:1))
      # works
      ggplot () + geom_text(data=labels_test,aes(b,c,label=a),color="blue")
      # does not work: 
      ggplot () + geom_text(data=labels_test,aes(b,c,label=a),color="blue",family="Times")
      # error message:  In grid.Call.graphics(L_text, as.graphicsAnnot(x$label), x$x, x$y,:
      # Font family not found in Windows font database
  </code></pre>
  
  <p>I already imported all fonts as indicated <a href="http://blog.revolutionanalytics.com/2012/09/how-to-use-your-favorite-fonts-in-r-charts.html">here</a>. Any ideas what is still going wrong?</p>