add raw level arg

[xgdgsc]

partly fix #52 .

I don' t find the "translate" necessary as users should know what they are actually using if they are trying to use a compression level.

[marcospb19]

Thanks for your contribution! We really do appreciate it, here's a small change request:

I see you're simulating Option<u32> behavior by using u32::MAX as a marker for None, instead, you can provide Option<u32>, clap will understand that it is optional and now we'll be able to see in the code that this flag is indeed optional, and maybe wasn't provided.

As Figsoda said, you can also take advantage of this and use Option's methods for default values, instead of doing if-else.

I also think it should be called --level.

[marcospb19]

I reviewed the compression levels for each format and three of them need adjustment:

[figsoda]

you might also want to allow clippy::too-many-arguments just to make clippy happy

[marcospb19]

Looks great, thanks!