tallty_import_export headers use symbel

lib/tallty_import_export/import.rb

@@ -23,7 +23,7 @@ module TalltyImportExport
       @primary_keys = options.delete(:primary_keys) || headers.map { |header| header[:primary_key] ? header[:key].to_sym : nil }.compact
 
       excel_hash = headers.reduce({}) do |h, header|
-        h[header[:key]] = header[:name]
+        h[header[:key].to_sym] = header[:name]
         h
       end