title: rename y axis text label in varImpPlot
body: <p>Is it possible to rename the y axis text label in <code>varImpPlot</code> of <code>library(randomForest)</code>?</p>
  
  <p>Here an example:</p>
  
  <pre><code>library (MASS)
  library(randomForest)
  set.seed (1)
  train1 = sample (1: nrow(Boston ), nrow(Boston )/2)
  rf.boston =randomForest(medv~.,data=Boston ,subset =train1 ,mtry=6, importance =TRUE)
  varImpPlot (rf.boston,n.var=4 )
  </code></pre>