Manage deployment

Hello,

As a developer, I would like to see deployment environments in Gitlab UI (https://gitlab.com/help/ci/environments/index.md).

I would like a function to create/update deployment using the [Gitlab API](https://docs.gitlab.com/ee/api/deployments.html#get-a-specific-deployment).

I suggest to add 2 functions like `gitlabDeployment()` and `updateGitlabDeployment()` (so it match the format of the `gitlabCommitStatus()` function).

And probably another one to fetch existing deployments.

wdyt?