code: function parseMappings(obj) {
          var mapping = {};
  
          // throw a helpful error when mapTwoWayState is mixed up with mapState
          if (Array.isArray(obj)) {
              error('Invalid arguments for mapTwoWayState. State mapping must be an object in { \'path.to.state\': \'mutationName\' } format.');
          }
  
          Object.keys(obj).forEach(function (key) {
              var value = obj[key];
              var vmKey = key.slice(key.lastIndexOf('.') + 1);
  
              if (typeof value === 'string') {
                  mapping[vmKey] = { key: key, mutation: value };
              } else {
                  mapping[vmKey] = { key: value.key, mutation: value.mutation };
              }
          });
  
          return mapping;
      }
docs: determine our key and mutation values