fixed: enable running upscale_elasticity compiled against MPI enabled libraries

make sure to call MPI_Init/MPI_Finalize.

the code still does not support MPI parallelization in any way, so
it halts if MPI_COMM_WORLD size is > 1.
Merge pull request #81 from akva2/fix_mpi

fixed: enable running upscale_elasticity compiled against MPI enabled li...

Merging directly since this currently breaks building.