Upgrade Finagle to version 6.24.0 (from 6.18.0)

Finagle changelog:
https://github.com/twitter/finagle/blob/master/CHANGES
fiangle-clojure-template: Add support for generating thriftmux projects

parse project-type from template cli args (defaults to thrift)

the interface for thrift and thriftmux is identical.
other project types in the future may differ and will require a refactor
of how template code is generated.
Add finagle-clojure-template thriftmux changes to changelog
thriftmux depends on thrift to know how to import thrift classes

at some point it may be worth deduplicating some more stuff between
thriftmux & thrift. for the moment i think it's ok as it makes it a
little easier to use thriftmux.

it might make sense conceptually for a thriftmux server to `serve`
a thrift `service` but that makes the API a little more complicated?