refactor: converting lodash map to es6 (#43)

converting lodash map to es6

Author: Esref Durna

src/stringifyTableData.js

@@ -1,13 +1,11 @@
-import _ from 'lodash';
-
 /**
  * Casts all cell values to a string.
  *
  * @param {table~row[]} rows
  * @returns {table~row[]}
  */
 export default (rows) => {
-  return _.map(rows, (cells) => {
-    return _.map(cells, String);
+  return rows.map((cells) => {
+    return cells.map(String);
   });
 };