Add _for_each_ref method
Reimplement Tag Hash Map in terms of for_each_rev
Reimplemnet tags_for_rev  in terms of tag_hash_map
Add get_tag method
Reimplent tags in terms of get_tag
Document new get_tag method
Add git report-version
Embolden basic test to be more squealy when things go bad
Style/Critic
Update Changes