bakery, httpbakery, bakery/checkers: stubs for new packages
httpbakery: add Service; unexport other types
bakery/example: update for new httpbakery API
httpbakery: start of Do implementation
improve doc comments
bakery, httpbakery: fix for macaroon changes
Merge branch 'master' of github.com:rogpeppe/macaroon into bakery
update README
Merge pull request #12 from rogpeppe/011-bakery-spike

bakery, httpbakery: new packages