Add align examples.

docs/_includes/examples/align.md

@@ -0,0 +1,5 @@
+# Align []({{ site.repo }}/blob/master/docs/_includes/examples/align.md)
+
+Use `align`, `halign` and `valign` options to set the alignment of the columns and their header. _by [@wenzhixin](https://github.com/wenzhixin)_
+
+<iframe width="100%" height="300" src="http://jsfiddle.net/wenyi/e3nk137y/17/embedded/html,result" allowfullscreen="allowfullscreen" frameborder="0"></iframe>