py: add initial conduit.relay.mpi module and tests (#542)

* py: add initial conduit.relay.mpi module and tests

* add docs and example python script for relay mpi

* update changelog

* relay mpi: skip py mpi tests on windows until we can get a sane ci setup

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project aspires to adhere to [Semantic Versioning](https://semver.org/s
 
 #### Relay
 - Added an open mode option to RelayIOHandle. See RelayIOHandle docs (https://llnl-conduit.readthedocs.io/en/latest/relay_io.html#relay-i-o-handle-interface) for more details.
+- Added the conduit.relay.mpi Python module to support Relay MPI in Python.
 
 ### Fixed
 

appveyor.yml

@@ -56,14 +56,17 @@ install:
   - conda install numpy
   # try to import numpy to as conda gut-check
   - python -c "import numpy as n; print(n.__version__); print(n.get_include());"
+  # try to import numpy to as conda gut-check
   # Install MS-MPI
   - ps: Start-FileDownload 'https://download.microsoft.com/download/B/2/E/B2EB83FE-98C2-4156-834A-E1711E6884FB/MSMpiSetup.exe'
   - MSMpiSetup.exe -unattend
   - set PATH=C:\Program Files\Microsoft MPI\Bin;%PATH%
-
   # Install MS-MPI SDK
   - ps: Start-FileDownload 'https://download.microsoft.com/download/B/2/E/B2EB83FE-98C2-4156-834A-E1711E6884FB/msmpisdk.msi'
   - msmpisdk.msi /passive
+  - set PATH=C:\Program Files (x86)\Microsoft SDKs\MPI;%PATH% 
+  # install mpi4py
+  - pip install mpi4py
 
   # Install CMake 3.9
   ############################################################################