v2.0.0

Breaking changes:

• Changed the format of serialized states (they no longer use a strict odd/even rule). Existing serialized states can be loaded by this version of the library but not vice-versa.
• Removed countBetween, _getAtCount, and fromEntries/fromKeys methods

New features:

• Embeds in SparseString

Misc:

• Major refactor of internals. This mostly simplifies the code, though it also slightly improves memory usage at the cost of slightly worse speed.