add kotlin support

[Gogomoe]

I'm failed to send the report to Coveralls
got following log:

:coveralls
service name: travis-ci
service job id: 246121223
repo token: present (not shown for security)
No source file found on the project: "ForeverNight"
With coverage file: /home/travis/build/gogo81745/ForeverNightEngine/build/reports/jacoco/test/jacocoTestReport.xml

Finally, I know the reason is that my project use kotlin only
refer to this

project.plugins.withType(GroovyPlugin) {
	targetSrcDirs += project.sourceSets.main.groovy.srcDirs
}

project.plugins.withType(ScalaPlugin) {
	targetSrcDirs += project.sourceSets.main.scala.srcDirs
}

But there is no kotlin here. That's why the plugin find no source file
So I add an additional configuration

coveralls {
    project.extensions.coveralls.sourceDirs += project.sourceSets.main.kotlin.srcDirs
}

It's like this

coveralls {
    sourceDirs += ['src/main/kotlin']
}

It is working now.
I hope to add support for Kotlin.

[kt3k]

PRs are welcome!

[Gogomoe]

Sorry , I am not familiar with gradle and groovy
In fact , I just started using gradle
I don't know how to fix it 😅

[kt3k]

This was duplicate of #63