Pony request, support for something akin to django orm's .extra()
Woohoo!!  Added!

http://charlesleifer.com/docs/peewee/peewee/querying.html#sql-functions-raw-expressions-and-the-r-object

Currently you are limited, more or less, to expressing select queries using the available abstractions - simple field queries, queries against column data (F objects), aggregations (min/max/count/etc), and aliases (foo as bar).  To go beyond that requires using the RawQuery, which exposes a stripped down interface.  Be nice to be able to add arbitrary elements to the select query to express things like "LOWER()" or other functions.  Also be nice to add it to the where() clause to express things like CASE statements and the like.
