Updates for new sagain api, s-c-build 3.1 and boot 2.6 (#243)

Updates releaser to use spring cloud build 3.1.0

Transitively uses boot 2.6

Updates releaser to use new Sagan API

Fixes gh-196
Fixes gh-194

releaser-spring/pom.xml

@@ -59,6 +59,11 @@
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.junit.vintage</groupId>
+			<artifactId>junit-vintage-engine</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 
 	<profiles>