Formatter deletes parenthesis around subqueries

[aosokin]

import mo_sql_parsing as msp
s = "SELECT count(*) FROM (SELECT city FROM airports GROUP BY city HAVING count(*)  >  3)"
d = msp.parse(s)
back = msp.format(d)
print(back)

This code produces SELECT COUNT(*) FROM SELECT city FROM airports GROUP BY city HAVING COUNT(*) > 3 where parenthesis disappear.

[klahnakoski]

Yesterday's work expanded the use of "precedence" to determine when parenthesis should be used. Now it is a matter of having enough tests to ensure I have the correct values set.

9978243#diff-77e357ea1ebd625dbc52532a43f82e67a856e499d3d0b1427b57a71c6f85056aR450