message: fix stylable.io relative github/twitter icons
diff: <a href="{{page.relative_root}}"><span class="logo"></span></a>
  <ul class="main-nav">
  - <li><a href="https://github.com/wix/stylable" target="_blank"><img src="/images/logo-git.svg" alt="Stylable on GitHub"></a></li>
  - <li><a href="https://twitter.com/stylableio" target="_blank"><img src="/images/logo-twitter.svg" alt="Stylable on Twitter"></a></li>
  + <li><a href="https://github.com/wix/stylable" target="_blank"><img src="./images/logo-git.svg" alt="Stylable on GitHub"></a></li>
  + <li><a href="https://twitter.com/stylableio" target="_blank"><img src="./images/logo-twitter.svg" alt="Stylable on Twitter"></a></li>
  </ul>
  </div>
  <script async src="https://www.googletagmanager.com/gtag/js?id=UA-109043375-1"></script>
  