title: Splitting strings with RegEx to match ampersand only when not surrounded by pluses
body: <p>I'm trying to split a query param string on <code>&amp;</code>s, as long as the ampersand doesn't have <code>+</code>s around it, but can't seem to get the RegEx right. My desired output for the example below is <code>["brand=dolce+&amp;+gabbana", "gender=male"]</code>.</p>
  
  <p>This is what I've tried:</p>
  
  <pre><code>str = "brand=dolce+&amp;+gabbana&amp;gender=male"
  str.split(/&amp;[^+&amp;+]/g)
  </code></pre>
  
  <p>This returns <code>["brand=dolce+&amp;+gabbana", "ender=male"]</code> which is close, but not quite right since the "g" in "gender" is getting matched as well. How can I ensure only the ampersands are matched?</p>