Lock Ruby 1.8 variants down to Nokogiri 1.5.x for travis testing.
Removing the allow_failures to see if it fixes the Gemfile matrix config.
Moved JAVA_OPTS to global environment to fix build matrix.
rbx-19mode should not use the 1.8.7 Gemfile.
ruby-head is failing when trying to install gems.  So it goes.
only modify /etc/hosts (and ask for sudo) if it has changed