title: ggvis, Error in normalizedPath()
body: <p>I am running one of the "interactive" examples from the ggvis webpage (<a href="http://ggvis.rstudio.com/ggvis-basics.html#introduction" rel="nofollow">http://ggvis.rstudio.com/ggvis-basics.html#introduction</a>) and I obtain an error. </p>
  
  <p>I loaded the ggvis, dplyr and shiny packages. </p>
  
  <p>Here is the code that I ran:</p>
  
  <pre><code>mtcars %&gt;% ggvis(~wt) %&gt;% layer_histograms(binwidth = input_slider(0, 2, step = 0.1))
  </code></pre>
  
  <p>And here is the output that I get. </p>
  
  <pre><code>Showing dynamic visualisation. Press Escape/Ctrl + C to stop.
  Error in normalizePath(directoryPath, mustWork = TRUE) : 
    path[1]="/Builds/CRAN-QA-Simon/packages/mavericks-x86_64/Rlib/3.1/ggvis/www/ggvis": No such file or directory
  </code></pre>
  
  <p>I am using RStudio Version 0.98.507, and R version 3.1.0; Platform: x86_64-apple-darwin13.1.0 (64-bit). </p>