Fix minor typo in Programming Kotlin description
Fix minor typo in Programming Kotlin description

Change "In is aimed at Java developers..." to "It is aimed at Java developers..." in the description for Programming Kotlin at http://kotlinlang.org/docs/reference
hltj/kotlin-web-site-cn,madvirus/kotlin-web-site,JetBrains/kotlin-web-site,belovrv/kotlin-web-site,hltj/kotlin-web-site-cn,meilalina/kotlin-web-site,TeamKotl/kotlin-web-site,madvirus/kotlin-web-site,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,TeamKotl/kotlin-web-site,TeamKotl/kotlin-web-site,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,belovrv/kotlin-web-site,meilalina/kotlin-web-site,hltj/kotlin-web-site-cn,madvirus/kotlin-web-site,meilalina/kotlin-web-site,meilalina/kotlin-web-site,hltj/kotlin-web-site-cn,belovrv/kotlin-web-site,JetBrains/kotlin-web-site