title: How to get query parameters in react-router v4
body: <p>I'm using react-router-dom 4.0.0-beta.6 in my project.
  I have a code like following:</p>
  
  <pre class="lang-jsx prettyprint-override"><code>&lt;Route exact path="/home" component={HomePage}/&gt;
  </code></pre>
  
  <p>And I want to get query params in <code>HomePage</code> component.
  I've found <code>location.search</code> param, which looks like this: <code>?key=value</code>, so it is unparsed.</p>
  
  <p>What is the right way to get query params with react-router v4?</p>