"macro" ember-cli blueprint

This isn't ready to merge yet, but I'd like some early feedback on the templates for the macro its self and the test

- [x] ember-cli creates a basic macro for `ember g macro <name>`
- [x] ember-cli automatically creates a test when generating the macro
- [ ] ember-cli alters `addon/ember-cpm.js` to register generated macros to the "EmberCPM" namespace
- [ ] squash commits before merging into master :) 
This file is  still very much WIP.