fix(lean-util): handle case where incomplete hierarchical name ends with "."

Close #311
fix(emacs/lean-mode): remove whitespace-cleanup-mode dependency

 - When customization variable 'lean-delete-trailing-whitespace' is
   non-nil, trailing-whitespaces are removed before save.

 - It doesn't change TABs.

Close #226
test(tests/lean/run): define below_rec_on (aka brec_on) for vectors
test(tests/lean/run): fibonacci using below_rec_on (aka brec_on)