Add support for python 3 (Only tested on 3.6 so far)

Description

Python 2 will eventually be discontinued. Also this allows for async and other functionality eventually if we ever move off 2.7

Unit tests were needed anyway, so I thought this was a good chance to add them to each module.

I've ported all the code (I think) to python 3, whilst still supporting python 2. There are still a lot of tests to write however to check it's working.

So far I've about half of Configuration done, MarketAnalysis was already done.

Opening this now for visibility in case anyone has comments or wants to help out.

You can run the test with

pytest -v

TESTING STAGE

Currently running this branch and testing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read CONTRIBUTING.md
• I fully understand Github Flow.
• My code adheres to the code style of this project.
• [N/A] I have updated the documentation in /docs if I have changed the config, arguments, logic in how the bot works, or anything that understandably needs a documentation change.
• [N/A] I have updated the config file accordingly if my change requires a new configuration setting or changes an existing one.
• I have tested the bot with no issues for 24 continuous hours. If issues were experienced, they have been patched and tested again.