docs: update badges

Readme.md

@@ -1208,13 +1208,13 @@ $ MYSQL_HOST=localhost MYSQL_PORT=3306 MYSQL_DATABASE=node_mysql_test MYSQL_USER
 * Prepared statements
 * Support for encodings other than UTF-8 / ASCII
 
-[npm-image]: https://img.shields.io/npm/v/mysql.svg?style=flat
+[npm-image]: https://img.shields.io/npm/v/mysql.svg
 [npm-url]: https://npmjs.org/package/mysql
-[node-version-image]: http://img.shields.io/node/v/mysql.svg?style=flat
+[node-version-image]: http://img.shields.io/node/v/mysql.svg
 [node-version-url]: http://nodejs.org/download/
-[travis-image]: https://img.shields.io/travis/felixge/node-mysql.svg?style=flat
+[travis-image]: https://img.shields.io/travis/felixge/node-mysql/master.svg
 [travis-url]: https://travis-ci.org/felixge/node-mysql
-[coveralls-image]: https://img.shields.io/coveralls/felixge/node-mysql.svg?style=flat
+[coveralls-image]: https://img.shields.io/coveralls/felixge/node-mysql/master.svg
 [coveralls-url]: https://coveralls.io/r/felixge/node-mysql?branch=master
-[downloads-image]: https://img.shields.io/npm/dm/mysql.svg?style=flat
+[downloads-image]: https://img.shields.io/npm/dm/mysql.svg
 [downloads-url]: https://npmjs.org/package/mysql