Added renew api call for Session service
Added renew api call for Session service

The renew API called as per documentation in Consul's HTTP API section: https://www.consul.io/docs/agent/http/session.html

Signed-off-by: 6eab1e768f8783074b241b2a7b09df39c4fd2013@gmail.com

sensiolabs/consul-php-sdk,sensiolabs/consul-php-sdk