python3 support, valid JSON output

[ghissues]

added a separate python3 file with valid JSON output and optional command line input

[aisbaa]

It seems that README file is not included into package

$ pip install git+https://github.com/ghissues/pyesprima.git
Collecting git+https://github.com/ghissues/pyesprima.git
  Cloning https://github.com/ghissues/pyesprima.git to /tmp/pip-xd14shhs-build
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-xd14shhs-build/setup.py", line 17, in <module>
        long_description=read('README'),
      File "/tmp/pip-xd14shhs-build/setup.py", line 5, in read
        return open(os.path.join(os.path.dirname(__file__), fname)).read()
    FileNotFoundError: [Errno 2] No such file or directory: '/tmp/pip-xd14shhs-build/README'