add genesis block; use genesis block header hash (#72)

Addresses # 71 - Unexpected zero hash for genesis header reported by @davxy
* chainspecs/blocks/genesis-tiny.json matches davxy's exactly and has 0x476243ad7cc4fc49cb6cb362c6568e931731d8650d917007a6037cceedd62244 header hash
* first block parent header hash is 0x476243ad7cc4fc49cb6cb362c6568e931731d8650d917007a6037cceedd62244 which is the header hash of the above

Author: sourabhniyogi