README: add release notes for 0.2.1
zpmlib: update version from 0.2 to 0.2.1
debian/changelog: 0.2.1-2 pkg update

This includes some changes that were missing in the original 0.2.1 pkg,
including release notes and the reported version on `$ zpm --version`.
Merge pull request #164 from larsbutler/v0.2.1-fixes

v0.2.1 fixes