some comments and layout changes for Trees.scala
some comments and layout changes for Trees.scala

MasseGuillaume/scalameta,DavidDudson/scalameta,olafurpg/scalameta,scalameta/scalameta,xeno-by/scalameta,scalameta/scalameta,MasseGuillaume/scalameta,scalameta/scalameta,xeno-by/scalameta,scalameta/scalameta,MasseGuillaume/scalameta,xeno-by/scalameta,scalameta/scalameta,Dveim/scalameta,olafurpg/scalameta,DavidDudson/scalameta,olafurpg/scalameta