message: updating spack install directions
diff: @@ -138,14 +138,6 @@ install one with Spack, for example
  $ spack load gcc
  $ spack compiler find
  -Now install the dependencies with your specified C++14 compiler (mine
  -will be gcc 7.2.0)
  -
  -.. code::
  -
  - $ (with MPI support) spack install boost+mpi+graph ^mpich %gcc@7.2.0
  - $ (without MPI support) spack install boost+graph %gcc@7.2.0
  -
  XACC has not yet been accepted into the Spack (we will soon issue a PR
  to get it shipped as part of Spack). So in order to install it with Spack
  we have to download our custom package recipe from the XACC repository:
  @@ -159,11 +151,7 @@ Now we can run
  .. code::
  - $ spack install xacc %gcc@7.2.0
  -
  -Once all these are installed, load them as environment modules
  -so they are available for the XACC build:
  -
  -.. code::
  + $ (without MPI support) spack install xacc
  + $ (with MPI support) spack install xacc +mpi
  + $ (with specified compiler) spack install xacc %gcc@7.2.0
  - $ spack load boost
  