Upgrade to maven-source-plugin 3.2.1

Closes gh-244

Author: philwebb

pom.xml

@@ -172,7 +172,7 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-source-plugin</artifactId>
-					<version>3.0.1</version>
+					<version>3.2.1</version>
 				</plugin>
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>