title: nvm install fails to Append nvm source string
body: <p>I downloaded NVM (on Mac High Sierra), with:</p>
  
  <pre><code>wget -qO- https://raw.githubusercontent.com/creationix/nvm/v0.33.11/install.sh | bash
  </code></pre>
  
  <p>download works, but then there's an error:</p>
  
  <pre><code>Appending nvm source string to /Users/User/.bashrc
  bash: line 353: /Users/User/.bashrc: Permission denied
  =&gt; Appending bash_completion source string to /Users/User/.bashrc
  bash: line 360: /Users/User/.bashrc: Permission denied
  </code></pre>
  
  <p>How can I grant it permission - or manually add the strings to .bashrc? And if so what does the string need to be?</p>