refactoring .travis.yml to use build matrix
refactoring .travis.yml to use build matrix

stan928/yum,edmunds-chef/yum,edmunds-chef/yum,xacaxulu/yum,ketan/yum,h4ck3rm1k3/yum,autotraderuk/yum,mattray/yum,ikkyotech/OpsworksNodeAddons,mrb/yum,stan928/yum,hippolin/yum-cookbook,xacaxulu/yum,ikkyotech/OpsworksNodeAddons,hippolin/yum-cookbook,xacaxulu/yum,GannettDigital/chef-yum,autotraderuk/yum,criteo-forks/yum,vkhatri/yum,hippolin/yum-cookbook,mattray/yum,mattray/yum,GannettDigital/chef-yum,someara/yum,criteo-forks/yum,chef-cookbooks/yum,h4ck3rm1k3/yum,mrb/yum,someara/yum,ketan/yum,someara/yum,vkhatri/yum,ketan/yum,juliandunn/yum,juliandunn/yum,edmunds-chef/yum,GannettDigital/chef-yum,stan928/yum,mrb/yum,vkhatri/yum,autotraderuk/yum,chef-cookbooks/yum,h4ck3rm1k3/yum