SelectButton demo missing directive

[ymajoros]

Hello,

So far very happy using this extremely powerful and outstanding library.

Just to let you know that the SelectButton showcase (http://www.primefaces.org/primeng/#/selectbutton) does not include SelectButton as a directive. Based on your quickstart demo on GitHub I was able to find out that this was required for it to work.

Autobots for the win!
Zord

[cagatay.civici]

Thank you for the great feedback.

I couldn't fine where the demo misses the directive? What should we add and to where? Thank you.