Fix leet option and some new options

[plmorale]

Hi, I came across your project and it came real handy for a research work that I was doing. I did some modifications, in case you are interested.

Namely I fixed the --leet option, I added --alloff, which is handy if you only want to use one or two options and don't want to type super long commands and I renamed the --allow-duplicates since I thought the name was confusing, it being a negative option.

[Minot1]

I saw this PR after I opened #15. Hope this gets pulled after 7 years :)