Merge branch 'demo'

Conflicts:
	src/main/java/captcha/configs/CaptchaConfig.java
	src/main/java/captcha/configs/WebConfig.java
	src/main/java/captcha/controllers/CaptchaController.java
	src/main/java/captcha/validators/CaptchaValidator.java
	src/test/java/captcha/controllers/CaptchaControllerTest.java