title: R - servr::jekyll() build error
body: <p>I am trying to use <code>jekyll</code> with <code>knitr</code> as proposed here </p>
  
  <p><a href="https://github.com/yihui/knitr-jekyll">https://github.com/yihui/knitr-jekyll</a></p>
  
  <p>When I try to use the <code>R function</code> (through R Studio) </p>
  
  <pre><code>servr::jekyll()
  </code></pre>
  
  <p>I get an error </p>
  
  <pre><code>sh: jekyll: command not found
  Error in jekyll_build() : Failed to run: jekyll build
  </code></pre>
  
  <p>There is no problem when building the <code>github</code> example, it works fine. 
  I have no idea where the error could come from. </p>
  
  <p>I work on a mac <code>OS X Yosemite</code>. </p>
  
  <p>Any clue ? </p>