moving attachToAdjacent method to onDetach()

Note that, if a Myo is already attached, the Myo SDK will attempt to reconnect automatically if there are disconnections. Also, if the attachToAdjacentMyo() function is called multiple times (with attached Myos) it can cause issues with other BT devices currently connected to the phone. This is currently being revised in the Myo SDK documentation as well.

In this case, I have made the assumption that we would like to be able to attachtoAdjacentMyo() as soon as the previous one has been detached.