Enable contract verification script to verify DAO contracts

[dkent600]

Enable contract verification script to verify DAO contracts such as Avatar, Controller, etc.

[dOrgJelli]

+1 would love if whenever someone calls "migrateDAO" they new contracts that're deployed are automatically verified. DAOcreator is looking for this functionality: dOrgTech/DAOcreator#191

I realize it requires an API key, so we could embed one in the application build and provide it as an argument to the "migrateDAO" function.