introduce TransientBlock for cleaner handling of unvalidated blocks
introduce TransientBlock for cleaner handling of unvalidated blocks

holiman/pyethereum,harlantwood/pyethereum,jnnk/pyethereum,ckeenan/pyethereum,shahankhatch/pyethereum,vaporry/pyethereum,shahankhatch/pyethereum,ethereum/pyethereum,karlfloersch/pyethereum,inzem77/pyethereum,ddworken/pyethereum,ethers/pyethereum,ethermarket/pyethereum,pipermerriam/pyethereum,pipermerriam/pyethereum,karlfloersch/pyethereum,ethereum/pyethereum