API for transitive dependency graph expansion, classpath creation

 tools.deps makes it simple and easy to interactively consume
 JVM libraries, without dragging in unrelated concerns of building programs
 or project management.
 .
 tools.deps will support package installers for Clojure (e.g. brew,
 apt-get, etc) to provide a path for Clojure installation and ongoing
 Clojure development.