Stateful path mapping module

[lukevenediger]

As a user I want to fire off steps to a state service and match them against a predefined path, firing a metric once a goal has been reached
So that I can track user paths without keeping state on my own service.

The gist of this feature is that callers use it to test assumptions about user movements and don't need to add state to their applications to do it. Think of this as a transformation of many incoming metrics to one or more outgoing metric. The incoming metrics are the individual steps while the outgoing metics are signals that certain workflow goals have been met.

Workflows are sent to the module before it acts on any new workflow steps.

For example,

Sending two workflows:
site.nav.home,site.nav.demo,site.nav.largeBanner,site.nav.signup:registration.newUser.fromLargeBanner|wf
site.nav.home,site.nav.demo,site.nav.linkOnLeft,site.nav.signup:registration.newUser.fromLeftLink|wf

Sending in steps
site.nav.home|wfs
site.nav.demo|wfs
site.nav.linkOnLeft|wfs
site.nav,signup|wfs
On the fourth step, statsd.net will send out a metric called
registration.newUser.fromLeftLink