Bump geth to v1.6.6
Bump geth to v1.6.6

Now including @konradkonrad's PR to fix the DAG generation problem: https://github.com/ethereum/go-ethereum/pull/14598

tomashaber/raiden,tomashaber/raiden,tomashaber/raiden,tomashaber/raiden,hackaugusto/raiden,tomashaber/raiden,hackaugusto/raiden