Multiple issues with DofMapPlotter

[oaniewiarowski]

Hi, I just installed fenicstools hoping it would help me debug some mesh mapping issues. However, right away I am having several issues with running the DofMapPlotter. I am using 2018.1 (conda-forge).

1. In 2018.1 mpi_comm_world() twas renamed to MPI.comm_world
2. I see that the test code has been commented out?
3. After fixing the mpi syntax, the demo fails on the call to dmp.plot(), error below

`dmp.plot(component=[0, n_dofmaps-2, n_dofmaps-1])
In file included from /Users/alexanderniewiarowski/fenics/fenicstools/fenicstools/dofmapplotter/cpp/.rendered.dmt.cpp:4:
In file included from /Users/alexanderniewiarowski/anaconda3/envs/fenics2018/include/python3.7m/pybind11/pybind11.h:43:
In file included from /Users/alexanderniewiarowski/anaconda3/envs/fenics2018/include/python3.7m/pybind11/attr.h:13:
In file included from /Users/alexanderniewiarowski/anaconda3/envs/fenics2018/include/python3.7m/pybind11/cast.h:13:
In file included from /Users/alexanderniewiarowski/anaconda3/envs/fenics2018/include/python3.7m/pybind11/pytypes.h:12:
/Users/alexanderniewiarowski/anaconda3/envs/fenics2018/include/python3.7m/pybind11/detail/common.h:140:10: fatal error: 'forward_list' file not found
#include <forward_list>
^~~~~~~~~~~~~~
1 error generated.
An exception has occurred, use %tb to see the full traceback.

SystemExit: error: command 'gcc' failed with exit status 1

/Users/alexanderniewiarowski/anaconda3/envs/fenics2018/lib/python3.7/site-packages/IPython/core/interactiveshell.py:3275: UserWarning: To exit: use 'exit', 'quit', or Ctrl-D.
warn("To exit: use 'exit', 'quit', or Ctrl-D.", stacklevel=1)`

[oaniewiarowski]

Also possible name conflict between module DofMapPlotter and class DofMapPlotter

ie should from fenicstools import DofMapPlotter be from fenicstools.DofMapPlotter import DofMapPlotter?