Don't run new or init inside of a generated ember-cli project

Solves the problem of by mistake running `ember new foo` or `ember init`, inside of a ember cli project.

To identify if we are inside of a generated ember cli project, it's looked the ember-cli dependency into package.json, this is performed recursivelly so if you are inside of my_app/tests or a my_app/node_modules directory, the project isn't created.