Changes:
- deprecated `invert_tree`, `squash_replace`, and `obfuscation_counts` from `multidecoder.query`. These will be removed in the next breaking version (v2)
- added a method `Node.flatten` in `multidecoder.node` with the functionality of `squash_replace` but as a method.
- added `pad_base64` to `multidecoder.decoders.base64` as a public function for base64 padding.