Remove js-delegatable-utils dependency on eth-simple-keyring

[danfinlay]

eth-simple-keyring depends on ethereumjs-wallet, which depends on the browserify polyfill for crypto, which means none of these modules work in an environment that doesn't polyfill the crypto module. That includes the latest create-react-app, or any lean webpack configuration. Removing that dependency will allow this module to live in leaner and more modern projects.