Using increment and measure on the same metric name in the same payload causes errors

[mbeale]

The Librato sink appears to combine the result into one gauge which causes an error of "value should not be set with count".

{"errors":{"params":{"value":["value should not be set with count"],"name":["***"]}}

The older version appeared to drop the measurement

ERROR:statsite.librato:Already stored metric's <cls.afw_entities_policy_evaluation.task.processed_entities> with a type doesn't coincide with incoming type . Source <***>. Skipping!