update README with token instructions (#4)

* copy readme over from devstats-data repo

* Make linter happy

---------

Co-authored-by: Jarrod Millman <jarrod.millman@gmail.com>

README.md

@@ -1 +1,34 @@
 # devstats
+
+This repository holds the devstats package. devstats uses the github API to
+generate developer statistics and a developer statistics report on a specified
+project.
+
+## OAuth key for accessing GitHub
+
+Per the [GitHub GraphQL API docs](https://developer.github.com/v4/guides/forming-calls/),
+you need a personal access token with `public_repo` permission to access the GraphQL API.
+
+This code expects the personal access token to be in the environment variable
+`GRAPH_API_KEY`.
+
+You can [create a personal access token](https://help.github.com/en/github/authenticating-to-github/creating-a-personal-access-token-for-the-command-line) on GitHub and save it somewhere you trust.
+Then, when you want to use the code: `export GRAPH_API_KEY=<yourkey>`
+
+## Query script
+
+The `query.py` script can be used to collect data for other projects like
+so: `python query.py <repo_owner> <repo_name>` where `repo_owner` and
+`repo_name` are the names of the **org** and **repo** on GitHub, respectively.
+
+First you need to install the required Python packages:
+
+```bash
+pip install -r requirements.txt
+```
+
+For example, to download the latest data for `pandas`:
+
+```bash
+python query.py pandas-dev pandas
+```