* Advance version, and drop Java 7 support
Advanced the version to 1.8.0 as Java 7 support is being removed.
* Remove build settings for Java 7
Removed the configuration for Java 7, and switched to trusty for access
to openjdk8.
Added the Travis CI configuration to enable continous integration
testing for common JDK version > 1.7.
Move gpg signing to its own profile to avoid causing issues with the
test, and integration-test phases.