add alerta client package to requirements
add alerta client package to requirements

skob/alerta,mrkeng/alerta,0312birdzhang/alerta,0312birdzhang/alerta,guardian/alerta,guardian/alerta,mrkeng/alerta,mrkeng/alerta,mrkeng/alerta,guardian/alerta,skob/alerta,skob/alerta,0312birdzhang/alerta,guardian/alerta,skob/alerta