please support new transactional check endpoints

[nergdron]

For transactional checks, there's a new set of GET endpoints to retrieve information about them. It'd be great if this library supported them as well:

https://api.pingdom.com/api/2.0/tms.recipes https://api.pingdom.com/api/2.0/tms.summary.performance/ https://api.pingdom.com/api/2.0/tms.summary.outage/ https://api.pingdom.com/api/2.0/tms.summary.average/