added methods and routes for getting an exercises history, and the sum of a workouts musclearrays -- incl a modifier

routes/middleware/load_workout.js

@@ -3,7 +3,7 @@ var workout = require('../../data/models/workout');
 function loadworkout(req, res, next) {
   console.log('fetch id' + req.params._id );
   workout.findOne({_id: req.params._id})
-    //.populate('elements')
+    .populate('elements.exerciseID')
     .exec(function(err, workout) {
       if (err) {
         return next(err);