chore(grunt): adds grunt-conventional-changelog plugin

this commit adds the awesome grunt-conventional-changelog plugin which
makes it possible to autogenerate changelogs based on the given
commit history

all you have to do is to follow some conventions

the plugin is used by angular.js itself and plenty other projects
Merge branch 'grunt-conventional-changelog-support' into grunt-conventional-changelog

* grunt-conventional-changelog-support:
  chore(grunt): adds grunt-conventional-changelog plugin

Conflicts:
	Gruntfile.js
	package.json
Merge branch 'develop' of github.com:goinstant/goangular into develop
Merge branch 'grunt-conventional-changelog' of github.com:PascalPrecht/goangular into PascalPrecht-grunt-conventional-changelog

Conflicts:
	Gruntfile.js
	package.json