Workaround subtle change in Regex#unapplySeq

We now hit a different overload and get back a `Vector[String]`,
rather than a `List[String]`. Our pattern match assumes `List`.

I've lodged a bug against Scala to improve the backwards
compatibility:

  https://issues.scala-lang.org/browse/SI-8022
Travis builds for 2.10.3 and 2.11.0-M7