Configure MySQL connector to log messages in slf4j.

See also: http://stackoverflow.com/questions/10903206/enabling-mysql-general-query-log-with-jdbc

Related to #420

Author: php-coder

src/main/resources/application-prod.properties

@@ -1,6 +1,6 @@
 spring.profiles: prod
 
-spring.datasource.url: jdbc:mysql://localhost:3306/mystamps
+spring.datasource.url: jdbc:mysql://localhost:3306/mystamps?logger=com.mysql.jdbc.log.Slf4JLogger
 spring.datasource.username: mystamps
 spring.datasource.password: q1
 spring.datasource.driver-class-name: com.mysql.jdbc.Driver

src/main/resources/application-travis.properties

@@ -1,6 +1,6 @@
 spring.profiles: travis
 
-spring.datasource.url: jdbc:mysql://localhost:3306/mystamps
+spring.datasource.url: jdbc:mysql://localhost:3306/mystamps?logger=com.mysql.jdbc.log.Slf4JLogger
 spring.datasource.username: travis
 spring.datasource.password:
 spring.datasource.driver-class-name: com.mysql.jdbc.Driver