fix typos
fetch-comments needs with-id fn to work
fix example by removing app arg to handle-submit

Fix example failing because up to tutorial 19, handle-submit only has 3 args
fix printing save-comment! result

http/post returns a map with :body which is where :message resides
reminder to pass opts to comment-form
Merge pull request #1 from cldwalker/doc-fixes

Doc fixes