Allow DiffSolver::continue_after_backtrack_failure
Merge pull request #89 from grinsfem/continue_after_backtrack_failure

Allow DiffSolver::continue_after_backtrack_failure
Add Nemesis output option
Runtime selection of Mesh/SerialMesh/ParallelMesh
Merge pull request #90 from grinsfem/nemesis_vis

Add Nemesis output option
Merge pull request #91 from grinsfem/parmesh

Runtime selection of Mesh/SerialMesh/ParallelMesh
Increase tolerances to pass stampede -np 2 tests

These are some fairly innocuous increases over some
previously-very-tight tolerances, so I think the right thing to do is
just loosen the tolerances.

This doesn't quite get "make check" working for me, though - there's
a 1e-2 scale error in a third test that might be an actual regression.
Merge pull request #92 from grinsfem/tolerances

Increase tolerances to pass stampede -np 2 tests