Closes#49
The /sources/{id}/monitored endpoint will return an array of Services
describing services this data source has monitoring data for.
The response has a `TagKey` and `TagValue` that can be used to specifically
query for the service.
This was generated using go-swagger's `swagger` command. The specific
command used was:
`swagger generate server -f swagger.yaml --with-context`
Fixes#6
Chris Goller
Will Piers
Tim Raymond