Package bitset implements bitsets, a mapping between non-negative integers and
boolean values. It should be more efficient than map[uint] bool.
It provides methods for setting, clearing, flipping, and testing individual
integers.
But it also provides set intersection, union, difference, complement, and
symmetric operations, as well as tests to check whether any, all, or no bits are
set, and querying a bitset's current length and number of positive bits.
