修改选择题题干类型（从string类型，修改为text）

Gemfile

@@ -15,7 +15,7 @@ unless RUBY_PLATFORM =~ /w32/
   gem 'nokogiri'
 end
 
-gem 'simple_xlsx_reader'
+#gem 'simple_xlsx_reader'
 gem 'wechat',path: 'lib/wechat'
 gem 'grack', path:'lib/grack'
 gem 'gitlab', path: 'lib/gitlab-cli'

db/migrate/20170918092326_modify_type_of_subject_for_challenge_chooses.rb

@@ -0,0 +1,8 @@
+class ModifyTypeOfSubjectForChallengeChooses < ActiveRecord::Migration
+  def up
+    change_column :challenge_chooses, :subject, :text
+  end
+
+  def down
+  end
+end