README tweak
wrap some long lines
clarify command parsing in ADAMMain
quote bash var
make `GenomicRegionPartitioner` a case class

seems like it’s well-suited to be one:
- public ctor vals
- boilerplate .equals method
- wrapper ctor that uses companion object method can go into companion
  object
remove no-op `remapContig` function

the “NM” comment about it being a no-op seems to be correct, afaict