title: How to customize nvd3's tooltips and remove labels from x axis
body: <p>I have this chart, but as you can see it has some problems:
  <img src="https://i.stack.imgur.com/F3sCW.png" alt="enter image description here"></p>
  
  <ol>
  <li>The tooltip height is wrong, there is that ugly blank space at the top. Since nvd3 has no documentation I really don't know how to proceed;</li>
  <li>The x axis labels are all overlapping, I want either to remove them or to tilt them (like 45 deg.). The second option is best. I also tried <code>.staggeredLabels(true)</code> but they still overlap.</li>
  </ol>
  
  <p>EDIT: I solved the second one by removing labels. Actually I don't remove them but rather hide them with:</p>
  
  <pre><code>.nv-x text {
      display: none;
  }
  </code></pre>