v3.1.0

• Added: sticky-footer.
• Added: angled-edges.
• Added: parallelogram.
• Added: drop-shadow.
• Improved: grid now works with @media query and can make several rows.
• Improved: rewrite container with css-calc, now you can combine container with other structure tags:

<header class="header container">
  <!-- Content -->
</header>

instead of separate them:

<header class="header">
  <div class="container">
    <!-- Content -->
  </div>
</header>

• Improved & fixed: simplify center and fix a layout broken issue while the content is wider than the container.
• Fixed: off-canvas submenu height issue.