20130129 - a health operation

[Dan Gravell]

I've added a non-chargeable 'health' operation to return the current health of the service. Clients can make calls to:

http://api.onemusicapi.com/beta/health?user_key=381a8738faaf39dd2be99d0827f035df

And "ok" will be returned if the service is operating normally. If the server cannot be connected to, no response is received (including after a timeout), or a different message is returned, the service is considered to be of poor health.

Dan