Update findbugs-maven-plugin from 2.5.2 to 2.5.5.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1628471 13f79535-47bb-0310-9956-ffa450edef68
Update cobertura-maven-plugin from 2.5.2 to 2.6.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1628472 13f79535-47bb-0310-9956-ffa450edef68