Improve assertion message in Violation
Add basic support for puppet-lint

This closes #21.
Add column support for puppet-lint

Though %{column} is not mentioned in --help text, it's supported in
version 0.3.2 and mentioned officially in 0.4.0.pre.
Beautify puppet-lint message
Merge branch 'puppet-lint'
Update changelog for 0.8.0
Prepare 0.8.0 release