Removed unused column in group by statement

lib/cartodb/models/dataview/histogram.js

@@ -169,7 +169,7 @@ var dateHistogramQueryTpl = dot.template([
     '    count(*) AS freq',
     'FROM ({{=it._query}}) _cdb_histogram, basics, bins, nulls',
     'WHERE date_part(\'epoch\', {{=it._column}}) IS NOT NULL',
-    'GROUP BY bin, bins_number, bin_width, nulls_count, avg_val, start_date',
+    'GROUP BY bin, bins_number, bin_width, nulls_count, avg_val',
     'ORDER BY bin'
 ].join('\n'));
 
@@ -180,7 +180,8 @@ var TYPE = 'histogram';
      type: 'histogram',
      options: {
          column: 'name',
-         bins: 10 // OPTIONAL
+         bins: 10, // OPTIONAL
+         aggregation: 'day' // OPTIONAL
      }
  }
  */