Survey reminder

Survey reminder notification functions
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File are edited:
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1) config/routes.rb
    Appended two post url

2) app/controllers/surveys_controller.rb

   Appended to new functions which are reminder and reminder_all

3) app/mailers/user_mailer
  Appended one mail function which is survey_reminder

4) app/views/surveys/stats.html.erb
   Appended "Send Reminder" button

New file:
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1) /app/views/user_mailer/survey_reminder.html.erb
    Static content which will be sent to user's inbox

Advantage:
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It is good for lecturer and students. Prompt notification: Less processing time: Alert student as many as you want; Able to send mass notification to everyone at a time; Able to send to one user at a time;