Update tutorial-13.md

KISS stands for [Keep It Simple, Stupid](https://en.wikipedia.org/wiki/KISS_principle).
Update tutorial-13.md

various typos and misspellings
Merge pull request #53 from taoeffect/patch-1

Update tutorial-13.md - corrected KISS acronym
Merge pull request #54 from taoeffect/patch-2

Update tutorial-13.md
small corrections
Merge branch 'master' of https://github.com/magomimmo/modern-cljs
small corrections
Grammar fixes to tutorial-14.