v2.0.0-beta.17

Changelog

• 67c481a Merge branch 'feat/refactor-message-types' into 2.x.x
• b71c9dc Merge pull request #251 from pact-foundation/feat/matt-plugin-example
• e6762d7 chore(release): release v2.0.0-beta.17
• 23c6dad docs(example): demonstrate matt plugin usage
• a810197 feat: upgrade verification to new FFI handles
• 5b1e094 fix: print mock server errors for sync messages with transport/mock server
• de50f1b fix: update consumer test header matcher
• 046a115 fix: upgrade to latest ffi 0.3.15
• 3c4c56f fix: verifier works multi-protocol