Add way to auto-add project dependencies

[PEZ]

clj-refactor has: cljr-add-project-dependency, this is huge when greenfielding https://github.com/clojure-emacs/clj-refactor.el/blob/master/clj-refactor.el#L2261

Originally posted by @bpringe in #137 (comment)

I think tools-deps is about to add dynamic loading by default, inspired by the add-libs3 branch. That is probably relevant to this idea.