Update plugins to current versions.
Update plugins to current versions.

maven-gpg-plugin ......................................... 1.4 -> 1.5
maven-surefire-plugin .................................. 2.16 -> 2.17
org.sonatype.plugins:nexus-staging-maven-plugin ............... 1.6.2

Minimum Maven version has been changed from 3.0 to 3.0.4 because it
is needed by the nexus-staging-maven-plugin.

wheelerlaw/system-rules,laurentleseigneur/system-rules,jdamick/system-rules