pip-install with Python 3 fails because of pyparsing version

Trying to `pip install cldoc` fails like [this](https://gist.github.com/cdeil/6fdbab3447dfc924d7a3#file-gistfile1-txt-L6)

The issue is that in `setup.py` you explicity put `install_requires=['pyparsing ==1.5.7'])` (see [here](https://github.com/jessevdk/cldoc/blob/master/setup.py#L148)

I already have  `pyparsing 2.0.3` on my system ... any reason you can't use that one and e.g. instead require `'pyparsing>=1.5.7'`?
```bash
$ python -c 'import pyparsing; print(pyparsing.__version__)'
2.0.3
```