title: how to find where homebrew temporarily saves dependencies being downloaded
body: <p>I'm installing <code>wkhtmltopdf</code> on my Mac using <code>homebrew install wkhtmltopdf</code> so it would go on like this: <code>Installing wkhtmltopdf dependency: qt</code>. 
  For some reason, my internet connection causes the download of a 200+mb file (<code>Downloading http://download.qt-project.org/official_releases/qt/4.8/4.8.5/qt-everywhere-opensource-src-4.8.5.tar.gz</code>) to only go at 4KB/s so I just copied my friend's version of the tar file.
  My OS version is Mavericks and QT does not support it yet so installing it separately will not work (already tried it).</p>
  
  <p>How would I be able to just copy the tar file and place it wherever brew stores temporary files or whatsoever, so that brew won't need to download it anymore? Specifically, where can I place the <code>tar.gz</code> file?</p>