Add health check route to API

[scriptnull]

We need this to check if API is alive

Just create a new route GET / and return the following payload

{
   "app": "badgeit-api",
   "version": "experimental"
}

[scriptnull]

Example of writing a new route in code can be found from https://github.com/scriptnull/badgeit/blob/master/api/main.go#L71