Document ngModel.$setValidity breaking change in the Changelog

[leefernandes]

At some point in the 1.3.x branch ngModel.$modelValues were set as undefined when invalid. I couldn't find this change documented in the changelog, but it did break validation in our case.

1.2.x behavior: http://codepen.io/ItsLeeOwen/pen/EfwKC
1.3.x behavior: http://codepen.io/ItsLeeOwen/pen/CwALx

[petebacondarwin]

Yeah I think you are right and to be honest if we are decoupling validation from parsing the validators should not be modifying the value but there is much more to it than that.