* implement in-memory block graph
* store tail block in database
* resolve unknown parents by syncing them from peers
* introduce concept of resolved blocks and attestations - those that
follow minimal protocol rules
* update state head lazily
* log more stuff
* shortHash -> shortLog
* start 9/10 beacon nodes by default, last can be started manually
* see also #134
* fix start.sh epoch length
* move attestation pool to separate file
* combine attestations lazily when needed
* advance state when there's a gap while attesting
* compile beacon node with optimizations - it's tooo slow right now
* log when unable to keep up
* use repeat_hash from spec in randao
* add some logging to state processing
* export crypto string converters in spec insulation layer
* enable block signature verification
* ssz: add support for arrays, remove custom data type code
* correctly handle previous and new block
* add trivial block processing tests
* prefer iterative repeat_hash
* state transition mostly done
* handle most specials and slashings