[MERGE] Add Support for `bzr tags -r 1..2`

[Jelmer Vernooij]

Jelmer Vernooij has voted tweak.
Status is now: Conditionally approved
Comment:
afaik _get2Revisions shouldn't have a capital R according to the style 
guidelines. It would be nice to have a docstring for that function as 
well. I think it would be more matching its behaviour if it was named 
"_get_revision_range".

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C418c22640812131939n782f4f59q39dc97cc53ac9e0c%40mail.gmail.com%3E
Project: Bazaar