Using Gradle 3.0, Kotlin 1.0.3, and the following build.gradle file, I get a compilation error:

Could not find method compileClient() for arguments [org.jetbrains.kotlinx:kotlinx.html.js:0.5.10] on object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

I get a different error if using "${kotlinx.html.version}" in place of the version number:

Could not get unknown property 'kotlinx' for object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

What I did get to work properly was calling the compile method on the js version of the library, but I doubt that the behavior is intended.

buildscript {
    ext.kotlin_version = '1.0.3'
    repositories {
       mavenCentral()
    }
    dependencies {
       classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

apply plugin: 'kotlin'

repositories {
    maven {
        url "http://dl.bintray.com/kotlinx/kotlinx"
    }
}

dependencies {
    compile "org.jetbrains.kotlinx:kotlinx.html.jvm:0.5.10"
    compileClient "org.jetbrains.kotlinx:kotlinx.html.js:0.5.10"
}