IOLoop.add_timeout requires an absolute time.

Autoclean

Log a warning when a result is leaked.

Typos and consistency

- Instead of catchig a bare exception, catch the two known exception types that could be thrown when adding a connection to a pool.
- Increase logging usefulness
- Don't resue the results variable that is used as an import for queries.results

- If too many simultaneous new connections are being made at the same time, it is possible that a pool can fill up by the time a connection is finally established when used asynchronously. This could cause leaked psycopg2 connections to occur when the PoolFullError is raised. To address this, the connection is closed prior to the error being raised. In addition, when closing the connection, make sure that if for any reason psycopg2 raises an exception, we handle that.
- Update all Queries exceptions to use a base QueriesException to they're easier to catch at a level that's isolated to the queries package.

Propagate exceptions from PoolManager.add.