Configure Travis CI to run PSR-2 code style checks
Configure Travis CI to run PSR-2 code style checks

Also configures Gitter integration.
Albert221/core,falconchen/core,Onyx47/core,kirkbushell/core,liukaijv/core,zaksoup/core,zaksoup/core,Onyx47/core,kidaa/core,kidaa/core,billmn/core,malayladu/core,Luceos/core,utkarshx/core,billmn/core,renyuneyun/core,flarum/core,vuthaihoc/core,huytd/core,jubianchi/core,Albert221/core,dungphanxuan/core,datitisev/core,datitisev/core,Luceos/core,billmn/core,Albert221/core,zaksoup/core,Albert221/core,dungphanxuan/core,datitisev/core,renyuneyun/core,malayladu/core,renyuneyun/core,Luceos/core,malayladu/core,Onyx47/core,liukaijv/core,jubianchi/core,falconchen/core,dungphanxuan/core,malayladu/core,flarum/core,flarum/core,kirkbushell/core,kirkbushell/core,huytd/core,vuthaihoc/core,datitisev/core,kirkbushell/core,Luceos/core,vuthaihoc/core,renyuneyun/core,utkarshx/core,kidaa/core,falconchen/core