Problem with playhouse.db_url.connect query params
Well, technically I think you can specify those using PRAGMAs, can't you? Or as manual params with `connect()`...

But isn't the `uri` aspect fairly new to pysqlite, or am I mistaken?
 It looks also like it's a Python3 only thing at the moment, added in 3.4, so I'm going to hold off on supporting that directly.
 Oh I wasn't aware of PRAGMAs, I'll take another look at this, thanks!
 After looking at this deeper, some options cannot be enabled via PRAGMAs, such as "shared cache". In this particular example, Python 2.x would have to use `sqlite3.enable_shared_cache(True)` module global, rather than specifying in the URLs. For this feature to have Python 2.x support, the `uri` module functionality would have to be [backported](https://hg.python.org/cpython/rev/f13bb1e40fbc), which is extremely difficult given that it's a `cpython` module. 

For anyone seeing this in future, if you're using Python 2.x then you're mostly outta luck. If you're using Python 3.x, then use `uri=True`.

Due to an outstanding [bug](https://bugs.python.org/issue24887) in sqlite3, some connection flags such as `mode=memory/cache=shared` can only be passed in via URI.

However, `playhouse.db_url.connect()` [converts](https://github.com/coleifer/peewee/blob/master/playhouse/db_url.py#L68) these query string parameters into `kwargs` for the database `connect()` call and are stripped from the URI, meaning that they are never actioned on.

As a temporary workaround for Sqlite3, you can bypass `db_url.connect()` and  use `SqliteDatabase` directly with `uri=True`, however it would be nice if it handled this stuff automagically.
