Issue-04 Change configuraiton to use a search path.

[nuvious]

Change configuration to use a search path. Also made a number of changes to support post-change testing and creation of a docker container for rapid testing.

Total changes include:

• Configuration search path that searches config/ ~/.gossip and ~/.config/gossip when attempting to load configuration files with an ENV variable available to override the search path. This is cross platform with ~ mapping to %USERPROFILE% in Windows
• Config file template is created
• Updates to modernize the use of setup.py and dividing up requirements into categories that can be installed optionally
• Updates to README and sphinx documentation
• Added a docker container to allow for rapid testing across different python versions
  • Added section in docs on how to use it
• Made some changes to make the code docker-ready