title: knit DT::datatable without pandoc
body: <p>I am trying to use <code>DT::datatable</code> to output a nicely formatted, interactive table in R.</p>
  
  <p>...only problem is that I want a heroku job to knit the document for me, and I've learned that RStudio and <code>rmarkdown::render()</code> use pandoc under the hood -- but pandoc doesn't ship in the stripped down <a href="https://github.com/virtualstaticvoid/heroku-buildpack-r/tree/cedar-14">R Buildpack</a> for heroku.</p>
  
  <p>Is there any way to get the old markdown engine (<code>knitr:knit2html</code> or <code>markdown:markdownToHTML</code>) to pass the javascript that powers <code>datatable</code> through?  Or to be more precise, to generate the sample table below <em>without</em> using pandoc?</p>
  
  <p>Here is a minimal example:</p>
  
  <p><strong>testing.Rmd</strong></p>
  
  <pre><code>---
  title: "testing"
  output: html_document
  ---
  
  this is a datatable table
  ```{r test2, echo=FALSE}
  library(DT)
  DT::datatable(
    iris, 
    rownames = FALSE,
    options = list(pageLength = 12, dom = 'tip')
  )
  ```
  
  this is regular R output
  ```{r}
  head(iris)
  
  ```
  </code></pre>
  
  <p><strong>knit_test.R</strong></p>
  
  <pre><code>require(knitr)
  knitr::knit2html('testing.Rmd')
  </code></pre>
  
  <p><strong>generates:</strong></p>
  
  <pre><code>this is a datatable table &lt;!–html_preserve–&gt;
  
  &lt;!–/html_preserve–&gt;
  this is regular R output
  
  head(iris)
  ##   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
  ## 1          5.1         3.5          1.4         0.2  setosa
  ## 2          4.9         3.0          1.4         0.2  setosa
  ## 3          4.7         3.2          1.3         0.2  setosa
  ## 4          4.6         3.1          1.5         0.2  setosa
  ## 5          5.0         3.6          1.4         0.2  setosa
  ## 6          5.4         3.9          1.7         0.4  setosa
  </code></pre>
  
  <p>desired behavior: have my datatable come through (not <code>&lt;!–html_preserve–&gt;</code>)</p>
  
  <p><strong>what I've tried</strong>
  I looked at htmltools and the <code>htmlPreserve</code> stuff but couldn't figure out how to apply that here.  did some crazy stuff with <code>saveWidget</code> that was not successful and does not bear repeating.</p>
  
  <p>Thanks!</p>