JSIEVE-111 Upgrade maven-assembly-plugin 3.0.0 -> 3.1.1
JSIEVE-111 Upgrade maven-assembly-plugin 3.0.0 -> 3.1.1

- Use goals `single` instead of `attached` by the recommendation at http://maven.apache.org/plugins-archives/maven-assembly-plugin-2.5.5/attached-mojo.html

apache/james-jsieve,apache/james-jsieve