Generate and attach dependency-tree

Update spring-boot-versions to generate a dependency-tree file and
attach it as an artifact. The file is generated by creating a temporary
POM and calling the invoker plugin.

The spring-boot-versions POM now depends on all spring-boot-starter-*
POMs to ensure that they have been installed before the dependency
tree is processes.

See gh-1047

spring-boot-dependencies/pom.xml

@@ -162,6 +162,12 @@
 				<groupId>org.springframework.boot</groupId>
 				<artifactId>spring-boot-starter</artifactId>
 				<version>1.1.0.BUILD-SNAPSHOT</version>
+				<exclusions>
+					<exclusion>
+						<groupId>commons-logging</groupId>
+						<artifactId>commons-logging</artifactId>
+					</exclusion>
+				</exclusions>
 			</dependency>
 			<dependency>
 				<groupId>org.springframework.boot</groupId>
@@ -292,6 +298,12 @@
 				<groupId>org.springframework.boot</groupId>
 				<artifactId>spring-boot-starter-test</artifactId>
 				<version>1.1.0.BUILD-SNAPSHOT</version>
+				<exclusions>
+					<exclusion>
+						<groupId>commons-logging</groupId>
+						<artifactId>commons-logging</artifactId>
+					</exclusion>
+				</exclusions>
 			</dependency>
 			<dependency>
 				<groupId>org.springframework.boot</groupId>