* Implement basic tree hash caching
* Use spaces to indent top-level Cargo.toml
* Optimize BLS tree hash by hashing bytes directly
* Implement tree hash caching for validator registry
* Persist BeaconState tree hash cache to disk
* Address Paul's review comments
* Change into_iter to iter
* Fix clippy 'easy' warnings
* Clippy eth2/utils
* Add struct NetworkInfo
* Clippy for types, utils, and beacon_node/store/src/iters.rs
* Cargo fmt
* Change foo to my_foo
* Remove complex signature
* suppress clippy warning for unit_value in benches
* Use enumerate instead of iterating over range
* Allow trivially_copy_pass_by_ref in serde_utils
