Confirm with the user before downloading mods

[DarkShadow44]

The problem

Sometimes it would be nice to now what mods have updates available, so I can check before updating them all.

My solutions

Add listing for all upgradable mods.

[Eskaan]

Add --pretend option to the upgrade subcommand

[DarkShadow44]

I assume this a suggestion how to implement it, not something that should already work?

[theRookieCoder]

Would be resolved by #49 Normally there will be a y/n prompt. If --force is used, it will download all the files no matter what, and if --dry-run is used, it will stop after version resolution and won't download anything.

[theRookieCoder]

Duplicate of #49