add sqlalchemy.async_query()

CHANGELOG.md

@@ -5,6 +5,9 @@
 + `sqlalchemy`: add `unbound_fk()`, `bound_fk()`
 + Add `sqlalchemy_async` module with `SQLAlchemy()` async database binding. 
     * Supports being used as an async context manager
+    * Automatically handles commit and rollback
++ `sqlalchemy_async` also offers `async_query()`
++ Changed `sqlalchemy.parent_children()` to use `lazy='selectin'` by default
 + Add `timed_cache()`, `TimedDict()`, `none_pass()`, `twocolon_list()`, `quote_css_string()`, `must_be()`
 + Add module `calendar` with `want_*` date type conversion utilities and `age_and_days()`
 + Move obsolete stuff to `obsolete` package (includes configparse 0.3 as of now)