Add Tag type for Action
Document public types and members
Merge pull request #6 from johnweldon/actions

Add Tag type for Action
clarify that Action Tag should be constructed from an Action Id not an Action Name
Merge pull request #8 from johnweldon/tweak

Clarify that Action Tag should be constructed from an Action Id ...
Merge branch 'master' of https://github.com/juju/names into 107-typed-news

Conflicts:
	tag_test.go