title: I got many warning and error when installing truffle
body: <p>I run the code 'npm install -g truffle' also tried 'npm install truffle',
  but the result is the same, here is the warning and error I got.
  When I try to install truffle, this show to me. I don't know how to fix it.</p>
  <p>Example:</p>
  <pre><code>npm WARN deprecated testrpc@0.0.1: testrpc has been renamed to ganache-cli, please use this package from now on.
  npm WARN deprecated safe-event-emitter@1.0.1: Renamed to @metamask/safe-event-emitter
  npm WARN deprecated mkdirp-promise@5.0.1: This package is broken and no longer maintained. 'mkdirp' itself supports promises now, please switch to that.
  </code></pre>