Amberflo-metering-python

Fixes:
- When uploading to S3, credentials do not work.
- Logging is not working when set to DEBUG
- uniqueId is not random if done within short interval of time
- S3 Filename logic is wrong, has special characters

Features:
- Add S3 ingestion client

- Added UsageClient
- Added CustomerApiClient
- Refactored MeterFactory to change message property names to camel case, updated names, and remove customer name.
- Added metering/samples for usage and customer

- Changed the `customer_id` and `customer_info` to be mandatory fields.

- Dropped support of Python versions before 3.5.
- Changed the `utc_time_millis` to be a mandatory field.

- Changed user/password authentication to an app_key.
- Small changes to the meter api:
- Change `tenant` to `customer_name` arg.
- Added a `customer_id` arg.
- Added a `unique_id` arg.
- `dimensions` is now a simple string to string map.
- Improved the meter api args validations logic.
- Removed the gzip app from the client api.
- Safer logging, and more robust client (handle exceptions better).
- Moved a few "responsibilities" to their own classes (logging, validation, meter message creation).
- Documented code and added unit tests.