Task and Extension have the same name, should be documented

[FibreFoX]

First of all, thanks for this plugin, it really helps (and yes, I do know the pain about documentation).

But I had some problem for creating task-dependencies inside my subprojects, the only hint was here: https://github.com/hierynomus/license-gradle-plugin/issues/77#issuecomment-127712381

I would suggest to add this hint into the README.md-file.

subprojects { subproject ->
    // https://github.com/hierynomus/license-gradle-plugin
    apply plugin: 'com.github.hierynomus.license-report'

    build.dependsOn(subproject.tasks.getByName('downloadLicenses'));

    downloadLicenses {
        // check transitive dependencies
        includeProjectDependencies = true

        // dependencyConfiguration = 'compile'
        dependencyConfiguration = 'runtime'
    }
}