Testing support for several Virtus Gems and Ruby versions
changing source of RubyGems URL
fix for TravisCI error of unknown folder
fix on gem dependency version notation
Keeping the initial situation with the gemfiles insite gemfiles/ folder
referencing gemspec path into Gemfiles
improving support to Virtus latest version
adjusts on CI settings
fix for Ruby 1.8.x support
removing old Ruby versions from build
New release: 0.2.3 [ci skip]