implement find_all_by_tag and find_all_by_tags on entities
implements #89 - add find_all_by_tag and find_all_by_tags on entities
Merge branch '89_entity_search_scopable_by_tags' of github.com:jessereynolds/flapjack into 89_entity_search_scopable_by_tags
merge master in, clean up a little
Merge pull request #94 from jessereynolds/89_entity_search_scopable_by_tags

89 entity search scopable by tags