Pre-commit root arg

[emdoyle]

Issue: #59

This allows users on the 'pre-commit' framework to adjust the root directory from which tach check will run during the pre-commit hook.

Example:

repos:
-   repo: https://github.com/Never-Over/tach
    rev: v0.1.8
    hooks:
    -   id: tach
    args:
    -   --root=backend