Tell user how many bits of entropy generated passphrase has

[sts10]

I'm curious if I should somehow inform the user of how "strong" their generated passphrase is, as measured by bits of entropy.

Pgen has an interesting way to do this.

Would welcome ideas! I could maybe eprintln! entropy information above the generated passphrase, hopefully preventing it from going to stdout?

[sts10]

This issue is less pressing since I added the minimum entropy option in 2297c37

[sts10]

This is now possible thanks to the new -v/--verbose flag. See #13 .