Change name of ember npm package in `after`

[kimroen]

This has landed now: emberjs/ember.js#13022

The name of the addon providing ember in the future is going to be ember-source, and so we need to addember-source inside after in the ember-addon-section of package.json to make sure we continue overriding the blueprints.

The section in question.

EDIT: Accommodate the suggestion by @locks.

[locks]

A small note that you might want to keep ember to make sure it works with versions of Ember older than v2.10 (the predicted release).

[kimroen]

Thanks, Ricardo! Good point, let's keep them both.