Link from CONTRIBUTING to setup documentation is dead

# Is this a feature request or a bug?
Bug (in the documentation)

# Expected behavior:
Following the link in [this section of the contributing guide](https://github.com/entropic-dev/entropic/blob/master/.github/CONTRIBUTING.md#project-setup) to [`the setup documentation`](https://github.com/entropic-dev/entropic/blob/master/.github/README.md) should lead to a document telling a new contributor how to set up the project.

# Actual behavior:
Link gives a 404.

I browsed around a bit looking for the correct destination but could not find any likely candidates.

# Steps to replicate:
In GitHub, navigate to `.github/CONTRIBUTING.md`, then try to click the link to the project setup documentation.

# Environment info (where relevant)

- Browser: Chrome 75.0.3770.142