v0.3.2 - bugfix large macrocycles

Another macrocycle bugfix.

Previously, rings larger than max_ring_size were added to the rigid_rings list. Bonds that belong to rings in the rigid_rings list are prevented from being broken. For large macrocycles, such as vancomycin, some rings larger than max_ring_size encompass smaller rings that must be broken. The bugfix consists in not adding rings larger than max_ring_size to the rigid_rings list. The rigid_rings list is exclusive for rings smaller than min_ring_size.

The behavior of max_ring_size in unchanged from the user perspective: rings larger than the specified value will not be opened. This is because rings larger than max_ring_size are not listed as breakable rings.

This bug came into existence after we started using an exhaustive set of rings instead of a smallest set of smallest rings (SSSR), after migrating from OpenBabel to RDKit.