readme: update to match c2a6bc443f78 (no Py3.2 support)
setup: be explicit about supported versions
readme: update changelog for version 0.2
readme: remove duplicate header

When the readme is shown on PyPI, the project description is inserted
right above the readme text. The description is also "ZeroVM Package
Manager", so if we don't delete it from the readme, it will appear
duplicated on the page.
Merge pull request #139 from mgeisler/zpm-0.2

README, changelog, and setup.py meta updates for zpm 0.2