…ions.from_dict()' (#943)

See https://packaging.python.org/guides/distributing-packages-using-setuptools/#universal-wheels

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [ ] Make sure to open an issue as a [bug/issue](https://github.com/googleapis/google-api-python-client/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

* Removing `.github/CONTRIBUTING.md`
* Creating new `CONTRIBUTING.rst` at the root of the repo that:
    * Links to the [Contribution Guide](http://googleapis.github.io/google-api-python-client/contributing.html) for basic housekeeping items such as CLA, Code of Conduct, Pull Requests, Style, Code Reviews.
    * Provides setup instructions and introduces Nox
* Modifying `README.md` to reference new `CONTRIBUTING.rst` 

Fixes: #963

Adding ability for discovery to retry on eligible http errors
and connection problems with randomized exponential backoff.

Also:
 * DRYing discovery tests to avoid warnings when reading test data.
 * Updating .gitignore

Fixes: #848

🤖 I have created a release \*beep\* \*boop\* 
---
## [1.10.0](https://www.github.com/googleapis/google-api-python-client/compare/v1.9.3...v1.10.0) (2020-07-15)


### Features

* allow to use 'six.moves.collections_abc.Mapping' in 'client_options.from_dict()' ([#943](https://www.github.com/googleapis/google-api-python-client/issues/943)) ([21af37b](https://www.github.com/googleapis/google-api-python-client/commit/21af37b11ea2d6a89b3df484e1b2fa1d12849510))
* Build universal wheels ([#948](https://www.github.com/googleapis/google-api-python-client/issues/948)) ([3e28a1e](https://www.github.com/googleapis/google-api-python-client/commit/3e28a1e0d47f829182cd92f37475ab91fa5e4afc))
* discovery supports retries ([#967](https://www.github.com/googleapis/google-api-python-client/issues/967)) ([f3348f9](https://www.github.com/googleapis/google-api-python-client/commit/f3348f98bf91a88a28bf61b12b95e391cc3be1ff)), closes [#848](https://www.github.com/googleapis/google-api-python-client/issues/848)


### Documentation

* consolidating and updating the Contribution Guide ([#964](https://www.github.com/googleapis/google-api-python-client/issues/964)) ([63f97f3](https://www.github.com/googleapis/google-api-python-client/commit/63f97f37daee37a725eb05df3097b20d5d4eaaf0)), closes [#963](https://www.github.com/googleapis/google-api-python-client/issues/963)
---


This PR was generated with [Release Please](https://github.com/googleapis/release-please).