Rollback message creation if ping no pings are sent
README updates, added twilio setup information
Merge pull request #32 from alxndrsn/readme-update

Added description of pingapp to the readme.
Merge pull request #34 from gr2m/master

README updates, added twilio setup information
Fix receiving of messages

* Use max id of the last ping to the recipient to get the Ping entry to
tag the Pong
Merge pull request #37 from ushahidi/fix-ping-retrieval

Fix ping retrieval