v0.8.0

Thanks to all the contributors for this release!

Changelog:

• Implement MPI_IN_PLACE operations (#232, @PhilipVinc )
• Add support for Cartesian process topology (#227, @samo-lin )
• Fixes to primitive type support (#223, @JaredCrean2 )
• Fixes to MPIManager (#222, #220 @christophernhill )
• Add support for shared memory windows (#221, @JobJob )
• Improved docs (#231, @jkozdon )
• Various smaller improvements (#233, @nolta; #224, @ziotom78 )