v1.8

This release stops FreeBuilder throwing IllegalStateExceptions when overwriting an entry in a map property, or attempting to remove an entry that is not there, bringing it in line with how the Map interface works.

FreeBuilder previously followed ImmutableMap.Builder's lead in throwing IllegalStateExceptions when putting an entry for a key already present in the map. As FreeBuilder types are frequently subject to modifications rather than always created from scratch, this has turned out to be a bad match for real-world usage. Since the behaviour is changing to be more permissive, i.e. to allow actions that would previously have thrown exceptions, this change is backwards-compatible.