message: Updates Axom's version in a RELEASE file (unintentionally not updated during the last release)
diff: *******************************************************************************
  -Axom: ................................, version 0.3.0
  +Axom: ................................, version 0.3.1
  Copyright (c) 2017-2019, Lawrence Livermore National Security, LLC.
  Produced at the Lawrence Livermore National Laboratory.
  