Configure external links in ScalaDoc
Configure external links in ScalaDoc

I found that Shapeless's [Scaladoc](https://oss.sonatype.org/service/local/repositories/releases/archive/com/chuusai/shapeless_2.11/2.3.1/shapeless_2.11-2.3.1-javadoc.jar/!/index.html) does not link to Scala standard library and other dependencies. This patch fixes the problem.
alexarchambault/shapeless,milessabin/shapeless,fthomas/shapeless,wheaties/shapeless,lambdista/shapeless,isaka/shapeless,lukasz-golebiewski/shapeless,khronnuz/shapeless,triggerNZ/shapeless