Do not panic on invalid input

[JayKickliter]

The upstream bloom crate we depend on panics when items_count == 0, bitmap_size == 0, fp_rate == 0.0, or fp_rate == 1.0. This would kind of makes sense, but only if it was documented, which it isn't.

To save debugging Erlang pattern mismatches, and remove the overhead of stack-unwinding, let's return an explicit error.