main: use the Words map

This is naive to begin with, as I know that the first position of the
Words map is the 😃 notation. Though since main.go is expecting
the colon notation, but could eventually get a Unicode codepoint, there
ought to be checking for this.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

main.go

@@ -174,7 +174,7 @@ func Sum(r io.Reader) ([]byte, error) {
 func emojiFromBytes(buf []byte) string {
 	var ret string
 	for _, b := range buf {
-		ret = ret + esum.Map(b)
+		ret = ret + esum.Map(b)[0]
 	}
 	return ret
 }