IE9 CSV loading fix (#1345)

* Fixes error parsing csv from xhr request callback object
* Fixes error in IE9 when parsing csv files. IE9 doesn't support response param of xhr callback object. Copy responseText param to response param fixed the issue. Charts now render correctly.

src/data.convert.js

@@ -11,15 +11,16 @@ c3_chart_internal_fn.convertUrlToData = function (url, mimeType, headers, keys,
     }
     req.get(function (error, data) {
         var d;
+        var dataResponse = data.response || data.responseText; // Fixes IE9 XHR issue; see #1345
         if (!data) {
             throw new Error(error.responseURL + ' ' + error.status + ' (' + error.statusText + ')');
         }
         if (type === 'json') {
-            d = $$.convertJsonToData(JSON.parse(data.response), keys);
+            d = $$.convertJsonToData(JSON.parse(dataResponse), keys);
         } else if (type === 'tsv') {
-            d = $$.convertTsvToData(data.response);
+            d = $$.convertTsvToData(dataResponse);
         } else {
-            d = $$.convertCsvToData(data.response);
+            d = $$.convertCsvToData(dataResponse);
         }
         done.call($$, d);
     });