Examples all fail silently with raised default gas

[wolflo]

Summary of the problem

The majority of manticore examples create contracts as follows:

user_account = m.create_account(balance=1000)
contract_account = m.solidity_create_contract(contract_src, owner=user_account, balance=0)

The default transaction gas is now 3000000, so solidity_create_contract fails silently (returns None) because the sender can't cover the gas.

Manticore version

0.3.4