title: Only require a module if it is installed
body: <p>Is it possible to tell if a module/package is available to use?</p>
  
  <p>Something like this:</p>
  
  <pre><code>var moduleexists = require "moduleexists"
  
  if (moduleexists("strangemodule")) {
    var strangemodule = require("strangemodule");
  
    strangeModule.doCoolStuff();
  } else {
    // Do something without strangemodule
  }
  </code></pre>