Install yarn using the recommended Ubuntu way
Install yarn using the recommended Ubuntu way

The npm way was working fine locally. This is an effort to make it work on
Travis where `yarn install` inside Docker fails with EEXIT, ENOTEMPTY etc.
errors.

NiGhTTraX/react-test-buffet,NiGhTTraX/react-test-buffet,NiGhTTraX/react-test-buffet