Spring + PostgreSQL > Multiple SLF4J bindings

Im currently trying to setup a Spring 4 / Hibernate 4 / PostgreSQL project. When I add the JDBC driver for PostgreSQL, i get following exception:

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/Users/Thomas/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-simple/1.7.7/8095d0b9f7e0a9cd79a663c740e0f8fb31d0e2c8/slf4j-simple-1.7.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/Users/Thomas/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-classic/1.1.2/b316e9737eea25e9ddd6d88eaeee76878045c6b2/logback-classic-1.1.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]

My application.properties file:

jdbc.driverClassName        = org.postgresql.Driver
jdbc.url                    = jdbc:postgresql://localhost:5432/itcareer
jdbc.username               = postgres
jdbc.password               = postgres
hibernate.dialect           = org.hibernate.dialect.PostgreSQL9Dialect
hibernate.show_sql          = true
hibernate.format_sql        = true
hibernate.hbm2ddl.auto      = update

HibernateConfiguration.java

package at.itcareer.config;

import java.util.Properties;

import javax.sql.DataSource;

import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.hibernate4.HibernateTransactionManager;
import org.springframework.orm.hibernate4.LocalSessionFactoryBean;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@EnableTransactionManagement
@ComponentScan({ "at.itcareer.config" })
@PropertySource(value = { "classpath:application.properties" })
public class HibernateConfiguration {

    @Autowired
    private Environment environment;

    @Bean
    public LocalSessionFactoryBean sessionFactory() {
        LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
        sessionFactory.setDataSource(dataSource());
        sessionFactory.setPackagesToScan(new String[] { "at.itcareer.model" });
        sessionFactory.setHibernateProperties(hibernateProperties());
        return sessionFactory;
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(environment.getRequiredProperty("jdbc.driverClassName"));
        dataSource.setUrl(environment.getRequiredProperty("jdbc.url"));
        dataSource.setUsername(environment.getRequiredProperty("jdbc.username"));
        dataSource.setPassword(environment.getRequiredProperty("jdbc.password"));
        return dataSource;
    }

    private Properties hibernateProperties() {
        Properties properties = new Properties();
        properties.put("hibernate.dialect", environment.getRequiredProperty("hibernate.dialect"));
        properties.put("hibernate.show_sql", environment.getRequiredProperty("hibernate.show_sql"));
        properties.put("hibernate.format_sql", environment.getRequiredProperty("hibernate.format_sql"));
        properties.put("hibernate.hbm2ddl.auto", environment.getRequiredProperty("hibernate.hbm2ddl.auto"));
        return properties;
    }

    @Bean
    @Autowired
    public HibernateTransactionManager transactionManager(SessionFactory s) {
        HibernateTransactionManager txManager = new HibernateTransactionManager();
        txManager.setSessionFactory(s);
        return txManager;
    }
}

gradle.build

buildscript {
    ext {
        springBootVersion = '1.2.1.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'
apply plugin: 'spring-boot' 

jar {
    baseName = 'portal'
    version = '0.0.1-SNAPSHOT'
}
sourceCompatibility = 1.7
targetCompatibility = 1.7

repositories {
    mavenCentral()
}


dependencies {

    // SPRING
    compile("org.springframework.boot:spring-boot-starter-data-jpa")
    compile("org.springframework.boot:spring-boot-starter-web") {
        exclude module: "spring-boot-starter-tomcat"
    }
    compile("org.springframework.boot:spring-boot-starter-jetty")
    compile("org.springframework.boot:spring-boot-starter-thymeleaf")

    // PostgreSQL
    compile 'org.postgresql:postgresql:9.4-1200-jdbc4'


    testCompile("org.springframework.boot:spring-boot-starter-test")
}

eclipse {
    classpath {
         containers.remove('org.eclipse.jdt.launching.JRE_CONTAINER')
         containers 'org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7'
    }
}

task wrapper(type: Wrapper) {
    gradleVersion = '1.12'
}