Succeed if `gimme stable` first cmd run
Succeed if `gimme stable` first cmd run

The `gimme stable` code-path was not ensuring that `~/.gimme/versions`
existed before creating the `stable` file within.

Fix, so that with no existing `~/.gimme` dir, `gimme stable` will work.

glevand/travis-ci--gimme,travis-ci/gimme,meatballhat/gimme,travis-ci/gimme,glevand/travis-ci--gimme