Refactored examples namespacing.
Refactored examples namespacing.

Refactored namespacing to be more consistent with the one used in the [Example](https://github.com/intridea/grape-entity#example): ``API::Entities::Status``, ``API::Entities::Address``, instead of ``API::Status`` or ``API::Address``, which look more like an API module.
dblock/grape-entity,calfzhou/grape-entity,iangreenleaf/grape-entity,geniousli/grape-entity,intridea/grape-entity,cakejelly/grape-entity,dan-corneanu/grape-entity,LeFnord/grape-entity,danhodge/grape-entity,marshall-lee/grape-entity,ruby-grape/grape-entity,tyre/grape-entity