Enhancement: Remove serve-favicon dependency

The philosophy behind the serve-favicon module is rather outdated, almost nobody knows or cares about creating .ico files. Everyone just puts .png or .gif files now (Mac and iOS ignore .ico anyway). But omitting the favicon.ico file makes the app crash in production environment because of the serve-favicon dependency.

Please consider removing this module and adding support for the modern icons required by the newer OSs, by adding these lines in _index.html:

  <link rel="icon" type="image/png" href="/favicon.png">
  <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
  <link rel="icon" type="image/png" sizes="96x96" href="/favicon-96x96.png">
  <link rel="apple-touch-icon" href="/favicon_120_retina.png">
  <link rel="apple-touch-icon" sizes="152x152" href="/favicon_152_retina.png">
  <link rel="apple-touch-icon" sizes="167x167" href="/favicon_167.png">
  <link rel="apple-touch-icon" sizes="180x180" href="/favicon_180.png">