Fix jmh -PjmhIncludeSingleClass

I would have assumed a JMH plugin update renamed include to includes,
but I don't see a mention to it in the plugin changelog. Either it was
an undocumented rename, or devs just kept fixing it locally and not
fixing upstream. In either case, it works now.

build.gradle

@@ -300,7 +300,7 @@ subprojects {
             // depends on core; core's testCompile depends on testing)
             includeTests = false
             if (project.hasProperty('jmhIncludeSingleClass')) {
-                include = [
+                includes = [
                     project.property('jmhIncludeSingleClass')
                 ]
             }