Set up express server and a bit more stuff, see comments

gitignores
-  yelp api keys file

adds yelp npm module

helpers.js
- helpers file to sends responses from server/ make http headers

server.js
- localhost:3000
- serves static files
- almost completes functionality for user's search post request to server and yelp api


yelp.js
- talks to yelp api! woooo