title: Restrict y-axis range on ggplot+geom_density
body: <p>I'm using geom_density to plot densities with very thin tails.  I want to restrict the y-axis range (so the top of the distribution will be off screen and the tail is more clearly visible) but it's throwing away data that is off-screen when it calculate the density, rather than just not showing what is off screen.</p>
  
  <p>E.g.</p>
  
  <p>This plots the full distribution,</p>
  
  <pre><code>testData = data.frame(counts=c(rep(1,5), 1:10))
  ggplot(testData, aes(x=testData$counts))+geom_density()
  </code></pre>
  
  <p>but when the y range is restricted, it looks as though the distribution has smaller support.</p>
  
  <pre><code>ggplot(testData, aes(x=testData$counts))+geom_density()+scale_y_continuous(limits=c(0,0.1))
  </code></pre>
  
  <p>How can I "zoom in" on the y axis without throwing away data?</p>