message: export the network classes
diff: @@ -14,7 +14,7 @@ const TX_BROADCAST_SERVICE_ZONE_FILE_ENDPOINT = 'zone-file'
  const TX_BROADCAST_SERVICE_REGISTRATION_ENDPOINT = 'registration'
  const TX_BROADCAST_SERVICE_TX_ENDPOINT = 'transaction'
  -class BlockstackNetwork {
  +export class BlockstackNetwork {
  blockstackAPIUrl: string
  broadcastServiceUrl: string
  layer1: Object
  @@ -442,7 +442,7 @@ class BlockstackNetwork {
  }
  }
  -class LocalRegtest extends BlockstackNetwork {
  +export class LocalRegtest extends BlockstackNetwork {
  constructor(apiUrl: string, broadcastServiceUrl: string,
  bitcoinAPI: BitcoinNetwork) {
  super(apiUrl, broadcastServiceUrl, bitcoinAPI, bitcoinjs.networks.testnet)
  