Override 'AS' in 'FROM table AS t1'
Interesting, I think this should be fixable but will require a quick code change.

``` python
    def parse_node(self, node, alias_map=None, conv=None):
        sql, params, unknown = self._parse(node, alias_map, conv)
        if unknown and conv and params:
            params = [conv.db_value(i) for i in params]

        if isinstance(node, Node):
            if node._negated:
                sql = 'NOT %s' % sql
            if node._alias:
                sql = ' '.join((sql, 'AS', node._alias))
            if node._ordering:
                sql = ' '.join((sql, node._ordering))
        return sql, params
```

Alternatively, you could subclass `QueryCompiler` and specify it in your subclass of `Database` that uses firebird's driver.  Can you share your firebird db class, btw? I'd be interested in integrating it into the `playhouse` module.
 Thank you for response! By the way, [my class](https://github.com/devsli/peewee-fdb/blob/master/peewee_fdb.py) is untidy now (I'm just learning Python). If you are interested, I'll let you know when it will become better.

Seems like 'AS' is hardcoded [here](https://github.com/coleifer/peewee/blob/master/peewee.py#L1179). Is it possible to override it in database subclass?

Firebird [doesn't use](http://www.firebirdsql.org/refdocs/langrefupd21-select.html) 'AS' for aliases.

EDIT: worksforme in firebird2.5 test case, need clarification
