Recommendation

Close #38 
Example Usage

    var testsesh = new RecSession('94103', 0, 3);

    // To initialize recommendations
    testsesh.buildRecommendation(function(recs){
      console.log(Object.keys(recs))
    });

    // To veto
    testsesh.veto({key:'id', val:'crepes-a-go-go-san-francisco-2'});
    testsesh.veto({key:'category', val:'asianfusion'});

    // Get recommendations
    testsesh.getRecs();