* On the testnet site, the first N instead of the last N validators
will be considered reserved for users
* The number of validators is consistently named `totalValidators`
in all commands
* Proper keys are generated by default in validator_keygen
* no need to pass prev_block_root when updating state
* some Slot fixes
* fix `hash_tree_root` for Slot, Epoch
* detect missing hash_tree_root type support
* remove some <0.5 state checks
* have regular slot tick, decide on work to do lazily
* use beacon clock instance that will eventually sync time
* skip work when falling behind
* add one more state cache for justified state (since that's used in
fork choice)
* remove old sync cruft
* single timer per slot, serializing block production and attestation
* ssz: update to 0.5.1:ish
* slightly fewer seq allocations
* still a lot of potential for optimization
* fixes#174
* ssz: avoid reallocating leaves (logN merkle impl)
* update processExits to 0.5.1
* mark process_deposit, get_empty_block as 0.5.1; update get_genesis_beacon_state to 0.5.1; implement processDeposits
* hotfix via https://github.com/ethereum/eth2.0-specs/pull/821
* rm gone-in-0.5.0 Proposal, verifyBlockSignature, and slot check which moved to spec function processBlockHeader
* mark get_attestation_participants and get_epoch_committee_count as 0.5.1; finish updating processAttestations to 0.5.1; add kludgy workaround for bug relating to get_winning_roots_etc using crosslink_data_root as index when we have that as ZERO_HASH for all leading to it confusing attesters on different shards; rm BeaconState.latest_attestations, which splits into previous_epoch_attestations and current_epoch_attestations
* Fix CI due to removed latest_attestations field
* add simple bitfield type (fixes#19)
* fix bit endianess to match spec
* consolidate attestation and block logging
* cruft cleanup
* run optimizer on tests, speeds up build
* begin refactoring 0.5.0 epoch transition at justification and finalization
* update processTransfers to 0.5.0 spec
* update get_crosslink_committees_at_slot to 0.5.0 except for noted workaround for pre-0.5.0 spec bug related to epoch boundary conditions, to be flipped in more coordinated way with other epoch processing changes
* mark ejection processing as 0.5.0
* 0.5.0 epoch update finalization
* rm BEACON_CHAIN_SHARD_NUMBER to complete updating miscellaneous constants to 0.5.0
* mark verify_slashable_attestation as 0.5.0
* update process_attester_slashing to 0.5.0
* update process_slashings(...) to 0.5.0 and mark process_exit_queue as 0.5.0
* refactor epoch processing by implementing 0.5.0's update_registry_and_shuffling_data(...)