update changelog for release 0.4.0
update changelog for release 0.4.0

pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-mock-server,pact-foundation/pact-reference,pact-foundation/pact-reference