Prep docs for indexing: remove stop words and punctuation, downcase, and stem (with fast_stemmer gem, a Ruby implementation of Porter's stemming algorithm)

sentence-prep.rb

#!/usr/bin/ruby

require 'rubygems'
require 'fast_stemmer'
stop_words = "a,able,about,across,after,all,almost,also,am,among,an,and,any,are,as,at,be,because,been,but,by,can,cannot,could,dear,did,do,does,either,else,ever,every,for,from,get,got,had,has,have,he,her,hers,him,his,how,however,i,if,in,into,is,it,its,just,least,let,like,likely,may,me,might,most,must,my,neither,no,nor,not,of,off,often,on,only,or,other,our,own,rather,said,say,says,she,should,since,so,some,than,that,the,their,them,then,there,these,they,this,tis,to,too,twas,us,wants,was,we,were,what,when,where,which,while,who,whom,why,will,with,would,yet,you,your,use,used".split(',')

unstemmed_words =  ARGV[0].gsub(/[[:punct:]]/, '').downcase.split.select { |x| !stop_words.include?(x) }
stemmed_words = []
unstemmed_words.each { |x| stemmed_words << x.stem }
puts stemmed_words.join(' ')