Add rubocop to travis build
Add rubocop to travis build

gchan/xruby,samilokan/xruby,mamenama/xruby,Insti/exercism-ruby,Insti/xruby,exercism/xruby,exercism/xruby,Calvyn82/word_count,Calvyn82/xruby,kotp/xruby,gchan/xruby,tommyschaefer/xruby,jdsayle/xruby,darrencauthon/xruby,alexbrinkman/xruby,NeimadTL/ruby,remcopeereboom/xruby,mamenama/xruby,wobh/xruby,kickinbahk/xruby,alexbrinkman/xruby,NobbZ/xruby,remcopeereboom/xruby,rashmiagar/exercism,Insti/exercism-ruby,NobbZ/xruby,jdsayle/xruby,NeimadTL/ruby,Insti/xruby,darrencauthon/xruby,Calvyn82/xruby,NeimadTL/ruby,kickinbahk/xruby,tommyschaefer/xruby,rashmiagar/exercism,Insti/exercism-ruby,Calvyn82/word_count,wobh/xruby,kotp/xruby,samilokan/xruby