Upgrade to Groovy 2.3.8

Closes gh-2021

Author: wilkinsona

spring-boot-dependencies/pom.xml

@@ -60,7 +60,7 @@
 		<freemarker.version>2.3.21</freemarker.version>
 		<gemfire.version>7.0.2</gemfire.version>
 		<gradle.version>1.6</gradle.version>
-		<groovy.version>2.3.7</groovy.version>
+		<groovy.version>2.3.8</groovy.version>
 		<h2.version>1.3.176</h2.version>
 		<hamcrest.version>1.3</hamcrest.version>
 		<hibernate.version>4.3.7.Final</hibernate.version>