Update nuspec change description.
Squashed commit of the 0.5.3.x branch:
Migrating MsTests to NUnit for reuse in added Universal81 (8.1 and WP8.1 Pcl) target. Universal81 implementation has introduced a few conditional compile hacks around reflection limitations but the MethodInfo.CreateDelegate behaviour seems good enough to try it out in the Beta wild.
Roll version forward to 0.6.0.*, tidy to standards, add lib\portable-win81+wpa81