Pydata-google-auth

* Respect the dirname and filename arguments to the ReadWriteCredentialsCache and WriteOnlyCredentialsCache constructors. (16, 17)

**Bug Fixes**

- Don’t write to the filesystem at module import time. This fixes an issue where the module could not be imported on systems where the file system is unwriteable. (10, 11)

- Add LICENSE.txt to package manifest. (https://github.com/pydata/pydata-google-auth/commit/c733c869aa688ec0b2b883bfcab8cdac418c89ed)
- Document privacy policy. (https://github.com/pydata/pydata-google-auth/commit/5378c79102b2e6dc83dfc6ea19f30f0a1a27bd23)

Initial release of pydata-google-auth, which is a fork of the authentication logic from the pandas-gbq package. This package assists in authenticating to Google APIs so that the credentials can be used in other packages, such as pandas-gbq, ibis, and the official google-cloud-python libraries.

* Use the [pydata_google_auth.get_user_credentials()](https://pydata-google-auth.readthedocs.io/en/latest/api.html#pydata_google_auth.get_user_credentials) function to get user credentials, authenticated to Google APIs.
* Use the [pydata_google_auth.default()](https://pydata-google-auth.readthedocs.io/en/latest/api.html#pydata_google_auth.default) function to get Application Default Credentials and fallback to user credentials when no valid Application Default Credentials are found.

See the full documentation at https://pydata-google-auth.readthedocs.io/en/latest/ for details.