Removed stl containers that pybind11 takes care of

Implemented basic buffer reading functionality
Added threading for bp serialization/deserialization
Refactored MPI functionality
Engine is now a reference
Initial Read API

Verified MPI and sequencial version

Removed IO Open that takes a new communicator (didn't work)

* Add initial python support to CMake build

* pybind11 2017-04-07 (1df91d36)

Code extracted from:

    https://github.com/pybind/pybind11.git

at commit 1df91d36cfa997c8987889234304ea5e37cc3e68 (v2.1.1).

* Build python bindings with cmake

* Adjust for adios2py -> adios2 module name

Applied autopep8 from python-pep8 for flake8 formatting in py

Issues:
Linking with Python 3.5 not working as-is with PyBind11
Passing a new communicator in IO Open fails (mpi4py?)

To do:
Add more test cases from other engines

To do:
Implement overloaded and default-argument class functions

Python bindings running but not printing values with bpls. Min and Max
captured correctly.

IO SetParameters and AddTransport will accept vector and map

Variable.cpp and Variable.tcc for complete separation of core components
in the public include