[ci-skip] update conversation example in the readme
[ci-skip] update conversation example in the readme

JoshSharpe/java-sdk,supunucsc/java-sdk,watson-developer-cloud/java-sdk,m2fd/java-sdk,JoshSharpe/java-sdk,watson-developer-cloud/java-sdk,supunucsc/java-sdk,watson-developer-cloud/java-sdk,m2fd/java-sdk,m2fd/java-sdk,watson-developer-cloud/java-sdk,JoshSharpe/java-sdk,supunucsc/java-sdk