v.0.3.0

Changelog:

• That's useful enough to release.
• Support passing parameters as a Hash.
• Ignore options that aren't applicable for the selected operation.
• Document create/update options.
• Allow template to be provided as data.
• Simplify tests a bit.
• Re-org exceptions.
• Add a more general ValidationError.
• Fix parameter support.
• Support YAML input.
• Improve README.
• Output JSON by default.
• Add template and parameters.
• The whole ErrorMappingProxy thing didn't really work out.
• Add "resources".
• Cleanup.