0.3.0

Changes

• Specify target state if transition method raises an Exception (#10)
• Only support Python 3.6+ (#13)
• Codecov Configuration (#14)
• Generate state machine diagram in Mermaid Markdown (#12)
• Handle transition function edge case when on_error is not set (#16)
• Add LICENSE file (#17)
• Upgrade to flit==3.0.0 (#18)
• bump version to 0.3.0