Build on Java 7 & 8

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Update semantic versioning enforcer rule

Signed-off-by: Sebastian Hoß <mail@shoss.de>
mention semantic versioning check

Signed-off-by: Sebastian Hoß <mail@shoss.de>
added link to mvn central

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Use nexus-staging-maven-plugin

Signed-off-by: Sebastian Hoß <mail@shoss.de>
[maven-release-plugin] prepare release superpom-1.0.7