title: R render Rd using roxygen2 without roxygen2 version
body: <p>Auto-documentation feature using roxygen2, while it is great and useful, it is annoying on every change of roxygen2 package version. It updates all my documentation files by putting roxygen2 version inside each file. See below.</p>
  
  <pre><code>% Generated by roxygen2 (4.1.1): do not edit by hand
  % Please edit documentation in R/src.R
  </code></pre>
  
  <p>Such changes obviously don't affect the code/package but did affect source control versioning by adding a noise to your source versioning process.<br>
  Could it be turned off somewhere?</p>