I've taken a look at the yelp library you are trying to use. It is made for use with Node.js. In general you can't just take a library created for use with Node.js and load it with RequireJS. In the best case scenario, you can convert a code-base made for Node.js into something that RequireJS uses by wrapping the code with define
calls.
Unfortunately, the best case scenario does not apply here because node-yelp actually uses some libraries specific to Node.js (for instance, querystring) and it calls on node-oauth which itself uses libraries specific to Node.js (for instance, crypto). To be able to use node-yelp with RequireJS you'd have to modify node-yelp and maybe node-oauth to be able to operate without the libraries that are specific to Node.js. This is a major undertaking.
Note here that it is possible to design a library for use with RequireJS and use in Node.js. (I've done it.) It's just that node-yelp was not designed this way.