Add dependency management for Postgresql

Closes gh-2545

spring-boot-dependencies/pom.xml

@@ -105,6 +105,7 @@
 		<mockito.version>1.10.19</mockito.version>
 		<mongodb.version>2.12.5</mongodb.version>
 		<mysql.version>5.1.34</mysql.version>
+		<postgresql.version>9.4-1201-jdbc41</postgresql.version>
 		<reactor.version>1.1.6.RELEASE</reactor.version>
 		<reactor-spring.version>1.1.3.RELEASE</reactor-spring.version>
 		<sendgrid.version>2.1.0</sendgrid.version>
@@ -1208,6 +1209,11 @@
 				<artifactId>mongo-java-driver</artifactId>
 				<version>${mongodb.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>org.postgresql</groupId>
+				<artifactId>postgresql</artifactId>
+				<version>${postgresql.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.projectreactor</groupId>
 				<artifactId>reactor-core</artifactId>