fix imports for examples
provide attributes for the artists associated with a release group
added api classes name plurals
Any class or class plural attributes for an entity are parsed as
Entities and cached in private attribute with the name of the entity api
class. The APIRelationship class will use the _ attribute as a cache
when loading and looking for relationships.
updated tests for the new auto-loading of cached relationships
added a Chart entity
example script using the chart entity
added a test for APIRealtionship
fixed bug with instances of APIRelationship being shared between instances of the same class
refactored ReleaseGroup to work with the new attribute loading method
Merge branch 'release/0.1.0'