Add CodeCov YAML file.
Add CodeCov YAML file.

This should make the output and statuses a bit more friendly.

nandub/brew,Homebrew/brew,claui/brew,sjackman/homebrew,nandub/brew,JCount/brew,vitorgalvao/brew,reitermarkus/brew,EricFromCanada/brew,EricFromCanada/brew,vitorgalvao/brew,reitermarkus/brew,konqui/brew,MikeMcQuaid/brew,vitorgalvao/brew,mahori/brew,sjackman/homebrew,sjackman/homebrew,mahori/brew,mahori/brew,MikeMcQuaid/brew,claui/brew,MikeMcQuaid/brew,reitermarkus/brew,Homebrew/brew,JCount/brew,EricFromCanada/brew,EricFromCanada/brew,mahori/brew,konqui/brew,JCount/brew,Homebrew/brew,reitermarkus/brew,konqui/brew,nandub/brew,JCount/brew,vitorgalvao/brew,sjackman/homebrew,MikeMcQuaid/brew,konqui/brew,Homebrew/brew,nandub/brew,claui/brew,claui/brew