support for scoped packages

[Dhaulagiri]

• Ensures that we can correctly create a nested directory in the event that a package's name is @myscope/package-name. This was breaking because the @myscope directory wasn't being created before.
• Ensures that we don't rely on matching names to be at the start of a package's name to allow for a scope to be at the beginning

Fixes #46, but I'm honestly not 100% sure if this is the best approach.
Fixes #111

[pzuraq]

Based on what’s going on in #111 I think I’d like to reduce the logo constraint even further. It should probably default to ember if nothing else is matched, and should have a manual override

[bravo-kernel]

Defaulting to the Ember logo would be awesome, much appreciated

[Dhaulagiri]

@pzuraq I updated my change to default to ember if there is no match on ember-cli or ember-data. Some local testing indicates that this now fixes #111 as well.

[pzuraq]

Awesome, thanks for taking this on!