Configure SimpleDateFormat to be strict during date parsing.

This change ensures that I don't do a mistake from c505b03 commit
again.

Addressed to #764

Author: php-coder

src/main/java/ru/mystamps/web/controller/SitemapController.java

@@ -54,6 +54,7 @@ public void getSitemapXml(HttpServletResponse response) {
 		response.setCharacterEncoding("UTF-8");
 
 		DateFormat dateFormatter = new SimpleDateFormat(DATE_FORMAT, Locale.ENGLISH);
+		dateFormatter.setLenient(false);
 
 		try {
 			PrintWriter writer = response.getWriter();

src/test/java/ru/mystamps/web/tests/Random.java

@@ -76,6 +76,7 @@ public static Date date() {
 		try {
 
 			SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
+			fmt.setLenient(false);
 			return between(fmt.parse("2017-01-01"), fmt.parse("2017-12-20")).date();
 
 		} catch (ParseException e) {