Update skolemize.py

[cestwc]

add a function, richardize (just a name trying to make it not confused with simplify or __reduce__ ), modified from skolemize.

The function name does not represent any logician Richard, and maybe the NLTK maintenance party can choose a better name.
The new function changes minimum from skolemize, and instead conversion to CNF (which is not equivalent but equisatisfiable to the input FOL expression), richardize(your_expr).equiv(your_expr) will be True.

The motivation of this function is that I did not find simplify to work in the way I wished, and for a pretty messy expression, e.g., those with a lot of consecutive negations, the new function can make it neater.

[stevenbird]

@cestwc: it looks like you've duplicated skolemize and made some changes to it. We need a well argued case for having (and maintaining) two similar functions. Could we please have more examples of different behaviours of the two functions? Is there a case for having both?

[zifuyang]

i second this