Duo-client

Changes:

- Minor fix up of string format
- Added support for SSO integrations operations
- Updated API authentication signing algorithm to Duo's preferred approach

Reverting the API authentication changes in 4.6.0 due to a bug.

Changes:
- Change from SHA1 to SHA512 for Duo API call authentication signing
- Fix various typos and comments
- Minor fix up of some code style issues
- Removed the deprecated constant PROTOCOL_SSLv23
- Added support for pending_deletion_days parameter for Settings operations
- Added support for SSO integrations operations
- Updated API authentication signing algorithm to Duo's preferred approach

- Add ability to update the status of Admins
- Add a way to get offline enrollment log events
- Add a way to get activity logs

- Update_settings method updated to match current API specification
- Allowed specifying a custom port for the client
- Added more trusted Duo CA certs to default bundle
- Cleaned up use of urllib/urlparse
- Fixed signature version 4 support
- Removed deprecated and unusable signature version 3 support

- Added support for Python 3.9
- Added a simple function in duo_client.Admin to fetch a single endpoint
- Added an example script using the Duo Trust Monitor Events iterator
- Added admin client methods for external password management API endpoints
- Removed extraneous Host header when running with Python 3