Drop Python 3.4 support and add mypy

[luk3yx]

From faeece4#commitcomment-33058422:

If you really want to prevent a lot of simple bugs, I recommend using type annotations with mypy, but this will probably require dropping support for Python <= 3.5. mypy can be annoying at first, but here is a sample config file for it to prevent its noise.

Resources:

• https://mypy.readthedocs.io/en/latest/cheat_sheet_py3.html

• https://docs.python.org/3/library/typing.html

[impredicative]

Apart from the config file, there are two ways that I personally know of and use to disable any irrelevant mypy messages:

• typing.cast
• "type: ignore" comment

[luk3yx]

For future reference, Ubuntu 14.04 / Linux Mint 17 machines (that should really be upgraded to a newer distro) can be updated with ppa:deadsnakes/ppa.

[luk3yx]

Currently, there are two ways of checking other mypy code against miniirc:

• Using miniirc.pyi (if I can somehow distribute this in the same PyPI package I will).
• Using miniirc_extras.AbstractIRC. This only works for IRC objects and not for other functions (such as Handler and CmdHandler).

[luk3yx]

Python 3.4 support will be dropped if/when I release miniirc v2.1.0.

I probably won't be adding mypy in miniirc itself until the minimum supported version is Python 3.6.