ClassTag.erasure => ClassTag.runtimeClass
ClassTag.erasure => ClassTag.runtimeClass

This change is made to be consistent with JavaMirrors.
And, in my opinion, a technology-neutral term is better here.

scala/scala-partest,lrytz/scala-partest,SethTisue/scala-partest,som-snytt/scala-partest,scala/scala-partest