Deprecation Warnings for `inspect.getargspec()` and `collections.abc`

[pyloolex]

Just a friendly reminder.

When I run tests through pytest on Python 3.8.10, I see warnings:

../home/vagrant/.local/lib/python3.8/site-packages/lollipop/compat.py:29
  /home/vagrant/.local/lib/python3.8/site-packages/lollipop/compat.py:29: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
    from collections import MutableMapping as DictMixin

../home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:46
  /home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:46: DeprecationWarning: inspect.getargspec() is deprecated since Python 3.0, use inspect.signature() or inspect.getfullargspec()
    arg_count = len(inspect.getargspec(func.__call__).args) - 1

../home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:42
  /home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:42: DeprecationWarning: inspect.getargspec() is deprecated since Python 3.0, use inspect.signature() or inspect.getfullargspec()
    arg_count = len(inspect.getargspec(func).args)

../home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:44
  /home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:44: DeprecationWarning: inspect.getargspec() is deprecated since Python 3.0, use inspect.signature() or inspect.getfullargspec()
    arg_count = len(inspect.getargspec(func.__init__).args) - 1

../home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:24
  /home/vagrant/.local/lib/python3.8/site-packages/lollipop/utils.py:24: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
    return isinstance(value, collections.Mapping)

-- Docs: https://docs.pytest.org/en/stable/warnings.html

I'm not creating a pull request since I'm not fully aware of what python versions are going to be supported. But it looks like some actions to resolve this are required.