Incorrect pyparsing compatibility notes in README

[ptmcg]

Note that you may encounter an error while installing pyparsing on which json2xlsx depends. This is probably because pyparsing 1.x runs only on Python 2.x while pyparsing 2.x runs only on Python 3.x. Currently, json2xlsx declares in the package that pyparsing 1.x is required, which means that Python 3.x users must install json2xlsx from GitHub with manual modificatin to setup.py. I do not use Python 3.x often, so please let me know a workaround.

Pyparsing 2.4.7 is compatible with both Python 2.7 and Python 3.x Pyparsing 3.0.0 is the first pyparsing version that is not compatible with Python 2.7.