Proposal: require API name

While apiblueprint.org is independent of apiary.io, I think some integration tools is going to use it for building blueprints that are going to be used in Apiary. 

Therefore, I think every blueprint that's valid on this API should be valid in Apiary as well. For this, I'd require blueprint name by default. 

I think we might later allow a way to override this through parameters. 

(This branch is build on top of #14)