Finalize transaction history

[bejitono]

The following items are still open for a first viable version for ETHDenver:

• Remove hard-coded address and connect to user settings to fetch the wallet’s tx history
• Handle different networks (for now mainnet/ropsten)
• Handle new confirmed transactions
• Possibly, handle pending transactions from the extension
  • For this we would need the Safari extension to pass transactions through the shared container so the containing app can start polling for transaction confirmation
• Show message on screen for empty transactions
• Follow up for the Zerion API key for the test flight version
• Fix async continuation issues when Zerion client tries to connect more than once (listenForConnections)
• Handle address and network changes