Add with-tags, tags-msg to add a tag set to :tags

Adds the with-tags macro to set tags for a scope.  The tags-msg
middleware is used to add the tags onto the :tags message key.

The :tags are not logged (by default).

Closes #2
Use the latest release of lein-pallet-release
Updated project.clj, release notes and readme for 0.1.2
Updated version for next release cycle