Add done_query methods to query traits

[d00z3l]

Hi @sunng87,

Another PR, this one adds done_query to the simple and extended handlers. The purpose is to allow clean up code to run after the query is successfully executed. I added default implementations so it doesn't break existing logic. Let me know if there is a better way to achieve this.

[sunng87]

@d00z3l Thank you for patch. After thinking about the case, I would recommend you to override on_query in your trait implementation for this behaviour. Because

1. Every method in simple/extended query handler is modeled by postgres messages. I feel that this type of query lifecycle callbacks should be at another level, like pre_query/post_query
2. For query_done, in order to make it useful we need to provide more context in addition to client.

So I would recommend you to keep it in your own implementation for now until we find common cases that we can build this query lifecycle layers.

[sunng87]

@d00z3l I just created a patch to address your concern in #287 . With this, you can override on_query and reference the default implementation with self._on_query(...), and add your own post_query logic in on_query.