Add requirements.txt to python script
Merge pull request #36 from kovrus/python-script-installation

Add requirements.txt to python script, facilitating easy installation of python pre-requirements using pip.
Add Ruslan Kovalov to the AUTHORS/CONTRIBUTORS files.
Refer to the json-c library as per their examples.

Not using -I makes more sense to me, but it appears that some distributions
put the headers in different locations, and all the example code refers only
to json.h, so we'll follow suit...

Also link against the correct library.