Add a pos_filters argument to keywords method
Add a pos_filters argument to keywords method

While the paper showed best performance was obtained with nouns and
adjectives, there are applications where including verbs, adverbs, or
even prepositions in the keywords list might be desirable.

quole/gensim,gojomo/gensim,summanlp/gensim,isohyt/gensim,tzoiker/gensim,piskvorky/gensim,dsquareindia/gensim,RaRe-Technologies/gensim,pombredanne/gensim,tzoiker/gensim,RaRe-Technologies/gensim,summanlp/gensim,loisaidasam/gensim,zachmayer/gensim,zachmayer/gensim,davechallis/gensim,isohyt/gensim,isohyt/gensim,laic/gensim,markroxor/gensim,loisaidasam/gensim,gojomo/gensim,robotcator/gensim,Kreiswolke/gensim,olavurmortensen/gensim,davechallis/gensim,quole/gensim,ELind77/gensim,dsquareindia/gensim,RaRe-Technologies/gensim,manasRK/gensim,jaksmid/gensim,ziky90/gensim,macks22/gensim,bhargavvader/gensim,olavurmortensen/gensim,ELind77/gensim,mattilyra/gensim,manasRK/gensim,pombredanne/gensim,akutuzov/gensim,mattilyra/gensim,mattilyra/gensim,ziky90/gensim,manasRK/gensim,robotcator/gensim,piskvorky/gensim,gojomo/gensim,jaksmid/gensim,robotcator/gensim,dsquareindia/gensim,olavurmortensen/gensim,laic/gensim,ELind77/gensim,piskvorky/gensim,akutuzov/gensim,loisaidasam/gensim,quole/gensim,macks22/gensim,summanlp/gensim,zachmayer/gensim,Kreiswolke/gensim,RaRe-Technologies/gensim,akutuzov/gensim,jaksmid/gensim,davechallis/gensim,bhargavvader/gensim,markroxor/gensim,pombredanne/gensim,tzoiker/gensim,gojomo/gensim,ziky90/gensim,laic/gensim,markroxor/gensim,macks22/gensim,bhargavvader/gensim,Kreiswolke/gensim