Broken import when using Python 3.7

[davebrown-exit107]

When attempting to use this package on Python 3.7, an error occurs:

(gremlin-python)[davebrown@codes gremlin-python]$ make test
python3 -m tests.test_all
Traceback (most recent call last):
  File "/home/davebrown/.pyenv/versions/3.7.10/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/home/davebrown/.pyenv/versions/3.7.10/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/davebrown/code/wk/gremlin-python/tests/test_all.py", line 7, in <module>
    from .test_httpclient import TestHttpClient
  File "/home/davebrown/code/wk/gremlin-python/tests/test_httpclient.py", line 9, in <module>
    from gremlinapi.config import GremlinAPIConfig as config
  File "/home/davebrown/code/wk/gremlin-python/gremlinapi/__init__.py", line 14, in <module>
    from gremlinapi.attack_helpers import (
  File "/home/davebrown/code/wk/gremlin-python/gremlinapi/attack_helpers.py", line 15, in <module>
    from typing import Type, Optional, Union, Dict, TypedDict, Any, Pattern
ImportError: cannot import name 'TypedDict' from 'typing' (/home/davebrown/.pyenv/versions/3.7.10/lib/python3.7/typing.py)
make: *** [Makefile:17: test] Error 1

It seems to be an easy fix, updating the import of TypedDict from typing-extensions instad of typing.