change output flag to dir flag

[khubo]

this changes the -o/--output to -d/--dir in decompress Command.

fixes #115

[marcospb19]

Thanks for your contribution!

I think this will get merged, but I'll need to wait a couple days beforehand, to see what other people thinking about that issue.

Expect a delay of at maximum 2 days.

[SpyrosRoum]

Even if this gets merged I think it might be best to wait for #108 first

[marcospb19]

@GabrielSimonetto pointed out that this would not let us have --output - anymore if we want to use STDOUT. But we have other possible solutions for that problem.

In last instance, /dev/stdout and /dev/stdin with --format can save us.

[marcospb19]

Thanks for the contribution and sorry for the late merge, I took some time to rest recently.