Eu criei uma instância do Postgre e com base nas informações do banco eu modifiquei meu persistence.xml, porém não adiantou.
https://www.dropbox.com/s/auj5itrr26eaq7o/Captura%20de%20tela%20de%202018-03-05%2023-41-24.png?dl=0
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
version="2.1">
<persistence-unit name="PedidoPU">
<description>
Persistence unit for Hibernate User Guide
</description>
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<properties>
<!-- Propriedades JDBC -->
<property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:postgresql://ec2-54-221-207-184.compute-1.amazonaws.com:5432/d4sshk8inoef2a" />
<property name="javax.persistence.jdbc.user" value="grsbtpmwdgdnpp" />
<property name="javax.persistence.jdbc.password" value="e77debb81451c1b99055971efa74ca3ac8275d474581afe68156c2e8d8e007e5" />
<!-- Configuracoes especificas do Hibernate -->
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.format_sql" value="false" />
<property name="hibernate.hbm2ddl.auto" value="update" />
</properties>
</persistence-unit>
</persistence>