adding method to create public folder if it does not exist

I tried to build the harmonic but gave the following error: 

root@debian:/home/jonatan/Documentos/github/harmonic# ./harmonic.js build
/home/jonatan/Documentos/github/harmonic/bin/parser.js:31
				if (err) throw err;
				               ^
Error: ENOENT, open './public/index.html'

then i added a function to check if the folder does not exist then it creates:

root@debian:/home/jonatan/Documentos/github/harmonic# ./harmonic.js build
Successefuly generate public folder
Successefuly generate index html file
Successefuly generate post html file hello-world
Successefuly generate post html file teste-post
Successefuly generate post html file teste