-I supports shell globs

[mgarciaisaia]

Fixes #1

[foca]

Thanks so much for taking the time and effort to do this! ❤️

Could you add tests for this? If not I'll get around to it probably over the weekend, but would like to merge with tests added.

[mgarciaisaia]

I'm really not that sure I could write a simple test around this - if you can come up with them, that'd be great 👍

[foca]

I added some tests and documentation on top of your changes on this branch. Feel free to pull them into the PR and I'll merge it 😄

[foca]

I also added a tiny performance improvement on top of your change, to avoid adding files to the search path, just directories. This way we pay a tiny penalty (checking if it's a directory) once when adding them to the path, but avoid iterating through a list with potentially lots of files each time you include another one.