title: add title using grid.arrange for multiple plots made with gridExtra::grid.arrange
body: <p>I have to use gridExtra::grid.arrange for plotting several plot besides eachother because of the package I am using to create the fit for the plot.
  I have to create a title for the plot using grid.arrange. 
  Now I want to combine the two, but cannot figure out how. So: I want to plot several figures besides eachother and give them all have a different title.</p>
  
  <p>I have euler1 and euler2 as fits tat represent my data in an euler diagram. 
  for plotting 2 plots besides eachother this code works for me: </p>
  
  <pre><code>gridExtra::grid.arrange(plot(euler1),plot(euler2))
  </code></pre>
  
  <p>for giving a single plot a title, this code works for me:</p>
  
  <pre><code>plot1 &lt;- plot(euler1)
  grid.arrange(grobs = list(plot1), top = "Title 1")
  </code></pre>
  
  <p>Now, I would like to combine the two codes.
  How can I do it?</p>
  
  <p>I tries for example (but doesn't work):</p>
  
  <pre><code>plot1 &lt;- plot(euler1)
  plot2 &lt;- plot(euler2)
  gridExtra::grid.arrange(plot1, plot2, grobs = list(plot1, plot2), top = list("Title 1","Title 2"))
  </code></pre>
  
  <p>Kinds regards,
  Judith</p>