Create initial Python package

[jklaise]

Initial structure for the Python package, mostly copying files from wrappers/python with a couple of bug fixes. Includes a conda recipe, tested conda build and install on local machine. Exposes the following entry points as console scripts:

seldon-core-microservice - start a microservice given a user defined model class
seldon-core-tester - test a running microservice by sending random requests following a pre-set format in contract.json
seldon-core-api-tester - test a running Seldon deployment

[jklaise]

TODO:

• Fix tests requiring access entry-point (i.e. package being installed)
  • pytest-console-scripts as a possible solution
  • pytest-reqs for testing against requirements.txt
• Get rid of seldon_requirements.txt
  • Make use of pinned dependencies in requirements.txt consistent
• "make build_conda" fails without doing "make build_pypi" first?
• conda-forge integration (manual)