Tracer now has an enabled flag
Option for logging instrumentation time
Added sampling size to tracer with default option of 1/1000 requests
Tracer now runs on a matching host if a regex is supplied
else runs on all hosts
Tracer now has an override flag so it can be switched on
or off at any time
No need for mocha yet. Going to refactor tracer run
logic into a runner class
Refactored decision logic about whether to run trace
into runner object