title: Yarn global command not working
body: <p>I'm working with Yarn v0.16.1. If I understand correctly (according to the <a href="https://yarnpkg.com/en/docs/cli/global" rel="noreferrer">documentation</a>), <code>yarn global add &lt;package&gt;</code> should be the equivalent of <code>npm install -g &lt;package&gt;</code>. However, when I run the example in the docs (with <code>create-react-app</code>), the command runs successfully but <code>create-react-app</code> is then not available from the command line. Here's the output:</p>
  
  <pre><code>$ yarn global add create-react-app
  $ yarn global v0.16.1
  [1/4]   Resolving packages...
  [2/4]   Fetching packages...
  [3/4]   Linking dependencies...
  [4/4]   Building fresh packages...
  success Installed create-react-app@0.6.0 with binaries:
    - create-react-app
  ✨  Done in 3.22s.
  $ create-react-app --help
  -bash: create-react-app: command not found
  </code></pre>
  
  <p>Doing a global install with npm has the expected result, and everything works. What am I missing with yarn?</p>