* allow running more or fewer validators
* use deterministic key generation for tests to avoid exhausting system
RNG
* update README with simulator docs
* write the data of each validator to separate file, instead of a big
chainstart.json (makes it easier to run different validator counts)
* 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
Jacek Sieka
Zahary Karadjov
Yuriy Glukhov