Cleanup ruby code via rubocop

This commit will add code cleanup as corrected
and alerted by rubocop. It also adds rules to
execute rubocop on Travis.

lib/facter/java_major_version.rb

@@ -13,8 +13,10 @@
 # Notes:
 #   None
 Facter.add(:java_major_version) do
+  java_major_version = nil
   setcode do
     java_version = Facter.value(:java_version)
-    java_patch_level = java_version.strip.split('_')[0].split('.')[1] unless java_version.nil?
+    java_major_version = java_version.strip.split('_')[0].split('.')[1] unless java_version.nil?
   end
-end
+  java_major_version
+end