title: Rstudio pdf knit fails with "Environment Shaded undefined" error
body: <p>When trying to knit a PDF using a template from package rticles <code>output: rticles::acm_article</code> I get the following error:</p>
  
  <pre><code>! LaTeX Error: Environment Shaded undefined.
  
  See the LaTeX manual or LaTeX Companion for explanation.
  Type  H &lt;return&gt;  for immediate help.
   ...                                              
  
  l.76 \begin{Shaded}
  </code></pre>
  
  <p>This appears to only happen when I include code chunks within the output document.</p>
  
  <p><strong>Reproducible example</strong>:</p>
  
  <p>You will need to start a new R Markdown document using the <code>New Document -&gt; From Template -&gt; Association for Computing Machinery</code>. Here is the R Markdown file:</p>
  
  <pre><code>---
  title: Short Paper
  author:
    - name: I Am Me
      email: me@email.com
      affiliation: Fictional University
  abstract: |
    This is the abstract.
    It consists of two paragraphs.
  output: 
    rticles::acm_article:
      keep_tex: true
  ---
  
  
  ## Simple test
  
  Code chuck follows:
  
  ```{r}
  plot(rnorm(10))
  ```
  </code></pre>
  
  <p>This above example, however, works if I set <code>echo=FALSE</code> in the header. You won't get code in the output, but for an academic paper you probably don't need it anyway, an if you do you can display it in a different manner.</p>
  
  <hr>
  
  <p>Notes:</p>
  
  <ul>
  <li>R version 3.3.1 (2016-06-21)</li>
  <li>Platform: x86_64-pc-linux-gnu (64-bit), </li>
  <li>running Ubuntu 16:10</li>
  <li>I made sure I have the texlive-latex-base, texlive-latex-recommended, and texlive-latex-extra package installed, but still no luck </li>
  <li>I also tried generating a pdf from the intermediate .tex file, as suggested <a href="https://stackoverflow.com/questions/36683670/compiling-latex-file-generated-by-rstudio">here</a>, but I get the same error.</li>
  <li>I considered <a href="https://stackoverflow.com/questions/34180355/pandoc-syntax-highlighting-in-pdf-not-working">this approach</a>, but it didn't work, I still got an error (maybe I need to tweak to work in my context, but not sure how) </li>
  </ul>