Update travis configuration
Update travis configuration

use sudo: false to enable container build
use cache: pip to cache pip packages

akretion/connector-telephony,brain-tec/connector-telephony,mohamedhagag/connector-telephony,alanljj/connector-telephony,intero-chz/connector-telephony,QuintoNetworks/connector-telephony,intero-chz/connector-telephony,akretion/connector-telephony,mohamedhagag/connector-telephony,treveradams/connector-telephony,credativUK/connector-telephony,brain-tec/connector-telephony,intero-chz/connector-telephony,mohamedhagag/connector-telephony,credativUK/connector-telephony,treveradams/connector-telephony,credativUK/connector-telephony,laslabs/connector-telephony,treveradams/connector-telephony,alanljj/connector-telephony,QuintoNetworks/connector-telephony,laslabs/connector-telephony,brain-tec/connector-telephony,laslabs/connector-telephony,akretion/connector-telephony,QuintoNetworks/connector-telephony,alanljj/connector-telephony