Add IoManager

0.10.0.0

Breaking Changes

• Drop support for Python 3.5
• Update GdbController() API. New API is GdbController(command: Optional[List[str]], time_to_check_for_additional_output_sec: Optional[int]).
• GdbController.verify_valid_gdb_subprocess() was removed
• Remove NoGdbProcessError error

Other Changes

• Add new IoManager class to handle more generic use-cases, like working with pty's
• [dev] use pytest for testing
• gdb mi parsing remains unchanged