Update Testing

[dmlb2000]

jsonpath2 version

v0.4.1

Platform Details

Travis CI

Scenario:

It would be nice to have testing on a more recent OS with newer versions of Python

Steps to Reproduce:

Make a pull request

Expected Result:

expected to get testing from Python 3.6, 3.7, and 3.8

Actual Result:

I only get testing from Python 3.6 and 3.7