Add bin/buildout --version

Fixes https://bugs.launchpad.net/zc.buildout/+bug/309770
Merge pull request #62 from mgedmin/buildout--version

Add bin/buildout --version
Typo fixes in the changelog
Mention that the ``buildout:unzip`` option was dropped

Fixes https://github.com/buildout/buildout/issues/94
Merge remote-tracking branch 'buildout/master' into header_expressions
Now supporting semicolon and hash comments.
Merge branch 'header_expressions' into buildout_21dev
Bump version to 2.1.0dev2