Quote possible shell wildcard

Because of this:
```
$ echo a[href*=boxscores]
a[href*=boxscores]
$ touch ah
$ echo a[href*=boxscores]
ah
```

README.md

@@ -24,7 +24,7 @@ Ew, HTML. Let's run that through some pup selectors:
 
 ```bash
 $ curl http://www.pro-football-reference.com/years/2013/games.htm | \
-pup table#games a[href*=boxscores] attr{href}
+pup table#games 'a[href*=boxscores]' attr{href}
 ```
 
 ## Basic Usage