memory use bugfixes
memory use bugfixes

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