Adds exception to AssetClassifier in case of multiple models. Fixes #476.
Adds the one_model? check to description_document_wrapper
so that the check is made before something is created with multiple models
Changes name of sample file with multiple models
Exception now displays all the models that returned true for the document
Merge branch 'development' into raise-exception-if-multiple-models-classified

Conflicts:
	spec/fixtures/pbcore/load_fixtures.rb
Adds missing comma
Merge pull request #549 from afred/raise-exception-if-multiple-models-classified

Failures are unrelated. I'm a bit uncomfortable with the complexity of the classifier and will try to sketch out something that would be simpler, I hope.