pip-friendly and better organization

- Added setup.py to make zpar pip installable
- Reorganized code to hide the ctypes stuff from the user and make zpar easier to use.
More pip-related changes.
Added error checking for uninitialized ZPar environment
Added comment about libptr garbage collection.
More changes.
Updated README and incremented version.
Added checks to make sure input files exist.
Fixed zpar_example.py
Removed redundant statment
Fixed path of test file in zpar_client.py
Added note about using CFFI.
Updated README.
Added conda.yaml file to build conda package.
Added note about conda to README.
Merge pull request #3 from EducationalTestingService/pip-friendly

Merging pip-friendly branch into master.