md-to-man.do: suggest how to install markdown/BeautifulSoup

...since they aren't included by default on MacOS X, but easy_install can
easily get them for you.

Documentation/md-to-man.do

@@ -3,5 +3,6 @@ if ./md2man.py </dev/null >/dev/null; then
 	echo './md2man.py $1.md.tmp'
 else
 	echo "Warning: md2man.py missing modules; can't generate manpages." >&2
+	echo "Warning: try this: sudo easy_install markdown BeautifulSoup" >&2
 	echo 'echo Skipping: $1.1 >&2'
 fi