adds internal write method and implements getSafeNode override in PersistedTree
updates dependencies, version bump
updates dependencies
fixes tests for PersistedTree.getSafeNode()
implements .getOrSetNode override in PersistedTree
fixes calling base methods in PersistedTree
implements PersistedTree.unsetNode() override
adds chaining tests to PersistedTree.setKey and .unsetKey
implements PersistedTree.unsetKey override