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

this plugin lets you auto-generate changelogs based on given commit
history

you commit messages have to follow the same conventions that are used
in this commit

for more information see http://github.com/btford/grunt-conventional-changelog
Merge branch 'grunt-conventional-changelog-support' of https://github.com/PascalPrecht/angularFire into PascalPrecht-grunt-conventional-changelog-support

Conflicts:
	Gruntfile.js
	package.json