Remove -r flag and use only -f flag

[toddbluhm]

Based on some user feedback common sense, the -r and -f flags are mutually exclused (can't be used at the same time), however they serve the same purpose, providing a custom file path.

Simply our flags by only using the -f flag to provide a custom path.

Now, if you provide a -e flag, the -f flag will assume you are pointing to a custom .rc file location.

Likewise if you use just -f it will assume you are pointing to a custom .env file path.

Resolves #359 and #372

[k-yle]

looks good, it'll be nice to simplify this. But I wonder if we should show a warning if somone upgrades to v11 and tries to use the -r flag, to make migration easier?

And I think we'll also need to update the README to remove -r

[toddbluhm]

That is a great idea to show the warning!

And great catch on updating the README, thought I had already done that.