bash syntax highlighting incorrect

not sure if this is the right place, but the bash syntax highlighter breaks if command substitution is done inside parameter expansion

``` bash
foo=${foo:-$(date | awk '{print $0}')}

# now everything is messed up
for f in ./*.js; do
 echo "$f"
done
```

The curly braces inside the awk command throw off the outside curly braces used around the variable it seems
