Update Software Licensing Grand Father renewal discount for 3.6 compatibility.

[cklosowski]

This snippet is out of date for people running 3.6+

http://library.easydigitaldownloads.com/extensions/software-licensing/grandfather-renewal-rate.html

The new code should be this: https://gist.github.com/cklosowski/15badf629336dbf19c87c8c1545e50d3

[brashrebel]

Thanks Chris! I'll get it updated real soon.