Sync finagle versions ( and all future versions )

Currently we have 3 storehaus modules that depend on finagle clients

- finagle-memcached 6.3.0
- finagle-redis 6.2.0
- finagle-mysql 6.2.1

This changeset syncs them to all to 6.3.0 and provides an common interface for doing so that reduces the build maintenance of keeping them in sync in the future 

```libraryDependencies += Finagle.module("foo")```