Add README (#3)

* black: reformat setup.py and make flake8 config compatible

* Add enough tests to ensure at least one test collected per shard

* more dummy tests!

* Draft README

* Address comments

* Update README.md

Co-Authored-By: Steven H. Wang <wang.steven.h@gmail.com>

Co-authored-by: Steven H. Wang <wang.steven.h@gmail.com>

README.md

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+[![CircleCI](https://circleci.com/gh/HumanCompatibleAI/benchmark-environments.svg?style=svg)](https://circleci.com/gh/HumanCompatibleAI/benchmark-environments) [![codecov](https://codecov.io/gh/HumanCompatibleAI/benchmark-environments/branch/master/graph/badge.svg)](https://codecov.io/gh/HumanCompatibleAI/benchmark-environments) 
+
+**Status**: alpha, pre-release.
+
+benchmark-environments is a suite of benchmarks for imitation-learning and
+reward-learning algorithms. It is currently a work-in-progress, but we intend for it to eventually
+contain a suite of diagnostic tasks for reward-learning, wrappers around common RL benchmark
+environments that help to avoid common pitfalls in benchmarking (e.g. by masking visible score
+counters in Gym Atari tasks), and new challenge tasks for imitation- and reward-learning. This
+benchmark suite is a complement to our  [https://github.com/humancompatibleai/imitation/](imitation)
+package of baseline algorithms for imitation learning.
+
+# Usage
+
+To install the latest release from PyPI, run:
+
+```bash
+pip install benchmark-environments
+```
+
+To install from Git master:
+
+```
+pip install git+https://github.com/HumanCompatibleAI/benchmark-environments.git
+```
+
+# Contributing
+
+For development, clone the source code and create a virtual environment for this project:
+
+ ```
+git clone git@github.com:HumanCompatibleAI/benchmark-environments.git
+cd benchmark-environments
+./ci/build_venv.sh
+pip install -e .[dev]  # install extra tools useful for development
+```
+
+## Code style
+
+We follow a PEP8 code style, and typically follow the [Google Code Style Guide](http://google.github.io/styleguide/pyguide.html),
+but defer to PEP8 where they conflict. We use the `black` autoformatter to avoid arguing over formatting.
+Docstrings follow the Google docstring convention defined [here](http://google.github.io/styleguide/pyguide.html#38-comments-and-docstrings),
+with an extensive example in the [Sphinx docs](https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html).
+
+All PRs must pass linting via the `ci/code_checks.sh` script. It is convenient to install this as a commit hook:
+
+```bash
+ln -s ../../ci/code_checks.sh .git/hooks/pre-commit
+```
+
+## Tests
+
+We use [pytest](https://docs.pytest.org/en/latest/) for unit tests
+and [codecov](http://codecov.io/) for code coverage.
+We also use [pytype](https://github.com/google/pytype) for type checking.
+
+## Workflow
+
+Trivial changes (e.g. typo fixes) may be made directly by maintainers. Any non-trivial changes
+must be proposed in a PR and approved by at least one maintainer. PRs must pass the continuous 
+integration tests (CircleCI linting, type checking, unit tests and CodeCov) to be merged.
+
+It is often helpful to open an issue before proposing a PR, to allow for discussion of the design
+before coding commences.