test_get_transaction_history() cover contract creation

[AndreMiras]

On contract creation the transaction dictionary has an empty a to field, but thecontractAddress is being filled up.
For example calling get_transaction_history() with address="0x02f8478cb5f78fdd702955a72e1895276765f482" will at some point fetch this tx https://etherscan.io/address/0x54c0de2318c89d598347b0000f26bad40c0ddf3b which is a contract creation.

This case needs to be unit tested. Also related to #141