add delete service
Merge branch 'deletepost'

Conflicts:
	src/main/java/com/minitwitter/controller/UserController.java
	src/main/java/com/minitwitter/service/TweetService.java
	src/main/java/com/minitwitter/service/TweetServiceImpl.java
	src/main/webapp/views/index.jsp
Merge branch 'master' of https://github.com/geeky-pikachu/minitwitter

Conflicts:
	src/main/java/com/minitwitter/controller/UserController.java