Update documentation: review chapter 4 and 5.

- chapter 4: Why do I not receive the deliveries?
- chapter 5: What is full text rss?
Update documentation: review chapter 6, 7 and 8.

- chapter 6: Can full text rss be processed as summary rss? What about
  the reverse?
- chapter 7: How to deal with weekly subscriptions?
- chapter 8: Can KindleEar deliver news to my kindle more than once a
  day?
Update documentation: review chapter 9, 10, 11

- chapter 9: How to use the url filter?
- chapter 10: What can I do if the gfw of China blocked some rss?
- chapter 11: How to put cover and masthead images in other directory
  when I add a builtin books?