Introduce cljr-insert-newline-after-require option

[vemv]

Context: clojure-emacs/refactor-nrepl#303

• The commits are consistent with our contribution guidelines
• You've added tests (if possible) to cover your change(s)
• The new code is not generating byte compile warnings (run cask exec emacs -batch -Q -L . -eval "(progn (setq byte-compile-error-on-warn t) (batch-byte-compile))" clj-refactor.el)
• All tests are passing (run ./run-tests.sh)
• You've updated the changelog (if adding/changing user-visible functionality)
• You've updated the readme (if adding/changing user-visible functionality)

[expez]

🎉

[vemv]

🍻!