Functions for creating and altering `com.twitter.finagle.Client` objects independent
of any particular codec. Generally speaking codec-specific client functions
should be preferred, but these are included for comptability with older systems
configured at the client level.

Functions for creating and altering `com.twitter.finagle.Server` objects independent
of any particular codec. Generally speaking codec-specific server functions
should be preferred, but these are included for comptability with older systems
configured at the server level.

Functions for creating com.twitter.util.Duration and com.twitter.util.Time.

Duration represents a length of time.
It can be use to express timeouts.
Functions such as [[finagle-clojure.futures/within*]] accept an explicit Duration object, while others
such as [[finagle-clojure.futures/within]] create one for you.

Wrapper around `com.twitter.finagle.Filter`.
Filters are like middleware and can be used to add funcionality common 
to many Services, like instrumentation or backpressure.

Filters are composed with other Filters or Services resulting in a Service.
Use `and-then` or `chain` to compose Filters & Services together.

Functions for creating & using `com.twitter.util.FuturePool`.
FuturePools can be used to run blocking code on a thread separate from Finagle.
This allows synchronous libraries to be used asynchronously in an application using Finagle.
A Future will be returned which allows for easy integration to other asynchronous Finagle code.

Functions for working with `com.twitter.util.Future` objects.
Futures are used to represent asynchronous operations in Finagle.

More info on the use of Futures (in Scala):
* https://twitter.github.io/finagle/guide/Futures.html
* https://twitter.github.io/scala_school/finagle.html

Functions for working with `scala.Option` objects.

Utilities for interop with JVM classes generated from Scala code.
Scala functions & methods expect Scala collection & function instances,
not Java Collections or Clojure IFns.

Functions for creating instances of com.twitter.finagle.Service.
Service is the main abstraction for both clients & servers.
It is where business logic is implemented.
Services can be created by using [[mk*]] & [[mk]],
or by proxying com.twitter.finagle.Service.

Service Services are often implemented with protocol specific helpers (see [[finagle-clojure.thrift/service]]).
Client Services are generated by protocol specific helpers (see [[finagle-clojure.thrift/client]]).

If creating an instance of Service with proxy
at least the apply method needs to be implemented.
Default implementations are provided for all other methods.

Instance methods of `Service` that can be overridden:
* (apply [req]) ; => Future[response]
* (close [time]) ; => Future[Unit]
* (isAvailable []) ; => boolean
* (map [fn1]) ; => Service[new-response-type]