Added readme file to serial interface project
Added readme file to serial interface project

ihassin/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,ihassin/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh