fix(travis): Try to fix diffing for PRs (also enable git checkout)
fix(travis): Try to fix diffing for PRs (also enable git checkout)

steffengy/zephir,zephir-lang/zephir,aaam/zephir,steffengy/zephir,dreamsxin/zephir,sjinks/zephir,zephir-lang/zephir,steffengy/zephir,steffengy/zephir,aaam/zephir,phalcon/zephir,phalcon/zephir,aaam/zephir,sergeyklay/zephir,phalcon/zephir,steffengy/zephir,aaam/zephir,sergeyklay/zephir,vpg/zephir,dreamsxin/zephir,sergeyklay/zephir,vpg/zephir,sjinks/zephir,vpg/zephir,zephir-lang/zephir,vpg/zephir,sergeyklay/zephir,sjinks/zephir,dreamsxin/zephir,dreamsxin/zephir,phalcon/zephir,phalcon/zephir,zephir-lang/zephir,zephir-lang/zephir,dreamsxin/zephir,sergeyklay/zephir,aaam/zephir,dreamsxin/zephir,vpg/zephir,sjinks/zephir,vpg/zephir,aaam/zephir,sjinks/zephir,phalcon/zephir,sergeyklay/zephir,steffengy/zephir,sjinks/zephir