Doesn't work with psql meta-commands & plpgsql syntax?

Hi! Noticed the following two issues when using `pgsanity`:

1. pgsanity seems to throw an error on the first line in this SQL code:
```
\set start 1234
delete from x where y >= :start;
```

2. Also doesn't seem to catch syntax errors in plpgsql code block:
```
DO $zzz$
dsafdsf
BEGIN
update test set id=4 where city='def';
END
$zzz$ LANGUAGE plpgsql;
```
