Method Timing should be moved to the agent

[janxious]

We no longer rely on the functionality inside Metrician for any of our other instrumentation and it's very different from the rest of the pieces in terms of configuration, other than having an enable flag, so probably it should be in the piece of tech that is built around the idea of full customization instead of automatic make do right.

[jason-o-matic]

We recently noticed that add_metrician_method_timer can have an issue if you use it on a class that gets loaded before metrician gets loaded, since it won't be defined yet. This could be another reason to move the method to the agent, though some care will still need to be taken with load order.

[jason-o-matic]

Actually my previous comment is more related to your current working directory when running the ruby process. https://github.com/Instrumental/metrician-ruby/blob/master/lib/metrician/configuration.rb#L32-L33 uses Dir.pwd to detect your app location, but if you run ruby from a different directory it won't current find your application metrician config.