DBT-693: Pre-commit checks for code quality and syntax, with python 3.7 support

[niteshy]

Describe your changes

Adding a pre-commit hook for code quality, and formatting configurations. Actual formatting changes are part of #169. These are kept intentionally separate so that configuration can be easily reviewable.
Formatting the code to use Python 3.7 or higher syntax

Internal Jira ticket number or external issue link

https://jira.cloudera.com/browse/DBT-693

Testing procedure/screenshots(if appropriate):

Checklist before requesting a review

• I have performed a self-review of my code
• I have formatted my added/modified code to follow pep-8 standards
• I have checked suggestions from python linter to make sure code is of good quality.