title: stringr::str_wrap does not wrap exactly every n characters
body: <p>The code below doesnt insert a new line after every third character which is what i thought str_wrap. Clearly there is some other underlying logic. I also get whacky results when the string contains some special characters. </p>
  
  <pre><code>t&lt;-c("The adds fundamental principle”, The discriminatory ")
  str_wrap(t,3)
  </code></pre>
  
  <p>the result is</p>
  
  <pre><code>&gt; str_wrap(t,3)
  [1] "The\nadds\nfundamental\nprinciple"
  </code></pre>