Add index argument to transformHeader (#807)

Author: furey

papaparse.js

@@ -1189,24 +1189,24 @@ License: MIT
 if (!_results)
 return;
 
-function addHeder(header)
+function addHeader(header, i)
 {
 if (isFunction(_config.transformHeader))
-header = _config.transformHeader(header);
+header = _config.transformHeader(header, i);
 
 _fields.push(header);
 }
 
 if (Array.isArray(_results.data[0]))
 {
 for (var i = 0; needsHeaderRow() && i < _results.data.length; i++)
-_results.data[i].forEach(addHeder);
+_results.data[i].forEach(addHeader);
 
 _results.data.splice(0, 1);
 }
 // if _results.data[0] is not an array, we are in a step where _results.data is the row.
 else
-_results.data.forEach(addHeder);
+_results.data.forEach(addHeader);
 }
 
 function shouldApplyDynamicTyping(field) {