f451: remove some dirty words and update the dictionary

tools/maint.md

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+# Maintainer notes
+
+Update `answer_words.txt` using `./update-words.sh`.
+

tools/update-words.sh

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+#!/bin/sh
+set +e
+
+url='https://rawgit.com/first20hours/google-10000-english/master/google-10000-english-no-swears.txt'
+getter="curl -sL"
+fn="answer_words.txt"
+
+filterer() {
+	grep '......*'
+}
+
+if ! curl -h >/dev/null 2>/dev/null; then
+	getter="wget -q -O -"
+elif ! wget -h >/dev/null 2>/dev/null; then
+	echo "[!] I don't know how to download. I need curl or wget."
+fi
+
+$getter "${url}" | filterer > ${fn}.tmp \
+	&& mv -f ${fn}.tmp ${fn}