title: Internal links in rmarkdown don't work
body: <p>I use rmarkdown to render pdf documents. Now I want to add internal links in the texts. </p>
  
  <p>In the helping pages of <a href="http://rmarkdown.rstudio.com/authoring_pandoc_markdown.html#links">rmarkdown</a>, it says an internal link is defined as:</p>
  
  <pre><code>See the [Introduction](#introduction).
  </code></pre>
  
  <p>When I Use e.g. the next code there should be two internal links: link1 and link2. Both don't link. Is there something obvious that I am doing wrong? Many thanks in advance!</p>
  
  <pre><code>   ---
  title: "Test"
  author: "test test"
  output:
    pdf_document:
      latex_engine: xelatex
      number_sections: yes
      toc: yes
      toc_depth: 3
    html_document:
      css: tables.css
      number_sections: yes
      theme: cerulean
      toc: yes
      toc_depth: 3
  subtitle: test test test
  mainfont: Calibri Light
  fontsize: 12pt
  header-includes:
  - \usepackage[dutch]{babel}
  - \usepackage{fancyhdr}
  - \pagestyle{fancy}
  - \fancyfoot[LE,RO]{this is a fancy foot}
  - \usepackage{dcolumn}
  - \usepackage{here}
  - \usepackage{longtable}
  - \usepackage{caption}
  - \captionsetup{skip=2pt,labelsep=space,justification=justified,singlelinecheck=off}
  ---
  
  # start
  
  ```{r results="asis",tidy=FALSE,eval=TRUE,echo=FALSE,message=FALSE, error=FALSE, warning=FALSE, comment = NA}
  cat("click here: [link1](#test 1)")
  ```
  
  click here: [link2](#test 1)
  
  \pagebreak
  
  #test 3
  
  \pagebreak
  
  #test 2
  
  \pagebreak
  
  #test 1
  </code></pre>