Add an example link.

[kanakiyajay]

Add a Demo page for easily seeing what the plugin does.
This was the link before :-

https://github.com/sderickson/treema/blob/master/test/test.html

[nwinter]

Scott has delivered! http://sderickson.github.io/treema/

[lc3t35]

Hum ! 404 There isn't a GitHub Page here. Can you fix please ?