v2.0.0

Fix

• Return a new ref instead of a borrowed one (b9b3730)
• Add missing exceptions.py module (5a1bfe0)
• Revert mypy (2ee28ca)
• Safely decref the pyobject that we use to store the state of agg initialization (fc70f1d)
• Use reset_init in finalize to indicate that the next step call should reinit (3dc3d54)
• Actually run constructors (8f02a99)
• udaf: Compile init functions (95fae29)

Breaking

• run constructors, which previously were not being called (8f02a99)

Documentation

• Add some docs, comments and fix types (3f476bf)
• Comment more on how byref works (4ed4cf0)

Performance

• Tell mypy to ignore tests because it's way too slow (86a8b62)