Datadog is a tool that allows you to send metrics that you create
dashboard and add alerting on specific behaviors.

Adding this contrib will allow for users of this tool to log their pipeline
information to Datadog.

Based on the status change of a task, we log that information to Datadog
with the parameters that were used to run that specific task.

This allow us to easily create dashboard to visualize the health. For
example, we can be notified via Datadog if a task has failed, or we can
graph the execution time of a specific task over a period of time.

The implementation idea was strongly based on the stale PR
spotify#2044.

I've also added a few test to ensure that the implementation was working
well.

This takes care of ensuring that the proper metrics collection calls are
being done when they are expected to be happening.

We've also removed a few `@RPC_METHOD` that weren't actually being used
and that wasn't required.

This makes sure that we're properly dispatching API and STATSD call with
the proper parameter values to Datadog.

This doesn't test all the different possible parameters configuration.

This adds a few extra documentation line for the configuration to allow
user to find all the settings they can tweak for each individual
contribs instead of having to go through each individual contrib files.

The original implementation was made when 0.16.0 was the latest version.
Since there there have been a few improvements and bug fixes made to the
library that we should be using.

Reading through the release log there shouldn't be any feature-breaking
changes so we should be good to update it!

Previously, the getter wasn't a class method and wouldn't work as
expected. In order to ensure that the output is what we expect, we've
added more tests.

There was multiple problems that needed to be solved in order to get the
specs green again. Each individual specs were passing when ran
individually, but when ran into tox as a group, some of them would pass
and other would fail depending the tox environment.

It came to my attention that the time function of this file, was
creating an issue with other specs because we were not tearDowning it as
expected. Also, using setTime within the setUp group had side effects
with unexpected behaviors.

Then, the way way that the task_id and task_family was named was also
causing problems with the same spec that were failing prior.  I'm unsure
why this would be the case, but changing either fail, but changing both
makes the spec to green.

Finally, the last spec would always fail because the setTime was set
AFTER the task was actually being run, which would always cause the
execution time to be greater than 0.

My understanding of all of this is still a bit fuzzy, but hey, now the
spec suite passes.

This will force people to implement this methods of this class when they
refer to it.

This allows for less-strict function calls.

The underlying configuration of the Datadog metrics collector is a
property, so it makes more sense that it's also a property when used
within the class itself.