Add multiple files support

[Yourun-proger]

resolves #94
I've added support for entering multiple arguments as files to check for complexity.
I also added handling of the case when the user does not enter anything as an argument for CLI.

[Yourun-proger]

Will there be any comments about this pull request?

[The-Compiler]

See #84, #73, #65 - you might want to use mccabe via flake8 (as intended) rather than a standalone tool.

[Yourun-proger]

Well, if this update is not needed, i can close this pull request. True, in this case, it is worth closing the original issue

[Yourun-proger]

Should this PR be closed?

[The-Compiler]

I'll leave that to whoever is maintaining this project - while a PyCQA member, I've never done anything in mccabe (I just happen to use it). But judging from there, the chances of this being accepted are probably slim, sorry.

[Yourun-proger]

Nevermind, I just wanted to hear some feedback) I guess I'll close this. If the maintainers still like it, they can reopen it. Thanks anyway!

[jrom99]

See #84, #73, #65 - you might want to use mccabe via flake8 (as intended) rather than a standalone tool.

Still, wouldn't it be better for it to raise more descriptive errors? IMO a ValueError or even TypeError in both cases would be more helpful than the current behavior or IndexError/ignore.