Update Kotlin tutorial to new edition(based on v1.3.50).
Update Kotlin tutorial to new edition(based on v1.3.50).

hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn