## Proposed Changes
Implement the consensus changes necessary for the upcoming Altair hard fork.
## Additional Info
This is quite a heavy refactor, with pivotal types like the `BeaconState` and `BeaconBlock` changing from structs to enums. This ripples through the whole codebase with field accesses changing to methods, e.g. `state.slot` => `state.slot()`.
Co-authored-by: realbigsean <seananderson33@gmail.com>
## Proposed Changes
Update test vectors for v0.12.3, and introduced configurable `proportional_slashing_multiplier`.
Also makes `YamlConfig` a bit safer by making every field access in `apply_to_chain_spec` explicit, and removing the `#[serde(default)]` attribute, which would instantiate missing fields to type defaults! Risky!
