Set provider_gem_name more logically
Set provider_gem_name more logically

The deployment provider's file name is identical to the
provider gem name by design, so it makes sense to use that value
instead of computed `name`.

computology/dpl,travis-ci/dpl,testfairy/dpl,testfairy/dpl,testfairy/dpl,travis-ci/dpl,travis-ci/dpl