doc/CHANGELOG: release notes for v0.9.0

doc/CHANGELOG: release notes for v0.8.0

doc/CHANGELOG: release notes for v0.7.1

doc/CHANGELOG: release notes for v0.7.0

doc/CHANGELOG: summary for v0.6.0

doc/CHANGELOG: summary for v0.5.0

doc/CHANGELOG: summary for v0.4.0

doc/CHANGELOG: summary for v0.3.0

doc/CHANGELOG: summary for v0.2.2

doc/CHANGELOG: initial commit