Removed the `serialport` package from the list of dependencies. It should be installed separately, if one wants to use the `SerialConnection`.
- Added `isOpen()` method to all `Connection` classes.
- Added `open` and `close` events to `UdpConnection` and `SerialConnection`.
Added `getConnection()` method to all `Transport` classes.
- Added `getTransport()`, `getConnection()` and `isConnected()` methods to `Master`.
- `Master` is now `EventEmitter`.
- `Master` now emits `error`, `connected` and `disconnected` events.
Updated the examples to reflect the recent changes to the `Master`.
Changed the options object for `createMaster()` to be entirely optional.
Fixed a copy-paste error in `Master.getConnection()`.
Fixed `TcpConnection`'s auto-reconnect.
Repeatable transactions are now paused if there's no connection and resumed when the connection is re-established.