title: Pretty axis labels for log scale in ggplot
body: <p>When I try either of the following the axis scale is 1e+03, 1e+06, 1e+09 - is it possible to get nice superscripted 10^3, 10^6, 10^9 instead without resorting to manual labelling?  I seem to recall getting this automatically in the past.</p>
  
  <pre><code>qplot(1:10, 10^(1:10))+scale_y_log10()
  qplot(1:10, 10^(1:10), log='y')
  </code></pre>