Reportportal-client

Added
- `RP` class in `reportportal_client.client` module as common interface for all ReportPortal clients, by HardNorth
- `reportportal_client.aio` with asynchronous clients and auxiliary classes, by HardNorth
- Dependency on `aiohttp` and `certifi`, by HardNorth
Changed
- RPClient class does not use separate Thread for log processing anymore, by HardNorth
- Use `importlib.metadata` package for distribution data extraction for Python versions starting 3.8, by HardNorth
- `helpers.verify_value_length` function updated to truncate attribute keys also and reveal attributes were truncated, by HardNorth
Removed
- Dependency on `six`, by HardNorth

Changed
- Unified ReportPortal product naming, by HardNorth
- `RPClient` internal item stack implementation changed to `LifoQueue` to maintain concurrency better, by HardNorth
Removed
- Unused `delayed_assert` dependency, by HardNorth

Added
- `launch_uuid_print` and `print_output` arguments in `RPClient` class constructor, by HardNorth
Removed
- Python 2.7, 3.6 support, by HardNorth

Added
- `__getstate__` and `__setstate__` methods in `RPClient` class to make it possible to pickle it, by HardNorth
Changed
- `token` field of `RPClient` class was renamed to `api_key` to maintain common convention, by HardNorth
Fixed
- Issue [214](https://github.com/reportportal/client-Python/issues/214): HTTP RFC compliance fix for getting project settings, by hanikhan

Added
- Check for parent `RPClient` object in thread before logging, by HardNorth

Added
- `RPClient.clone()` method, by HardNorth
Fixed
- Client crash in case of Client ID reading error, by HardNorth