Remove unused imports.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/trunk@1627979 13f79535-47bb-0310-9956-ffa450edef68
Add missing '@Override' annotations.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/trunk@1627980 13f79535-47bb-0310-9956-ffa450edef68