Add new Cask for gitlab 'lab' cli tool v0.10.1

[webframp]

Lab is a complementary tool, similar to Hub, that wraps git and allows
interacting with repositories hosted on a Gitlab server

After making all changes to the cask:

• [ X ] brew cask audit --download {{cask_file}} is error-free.
• brew cask style --fix {{cask_file}} reports no offenses.
• [ X ] The commit message includes the cask’s name and version.

Additionally, if adding a new cask:

• [ X ] Named the cask according to the token reference.
• [ X ] brew cask install {{cask_file}} worked successfully.
• [ X ] brew cask uninstall {{cask_file}} worked successfully.
• [ X ] Checked there are no open pull requests for the same cask.
• [ X ] Checked the cask was not already refused in closed issues.
• [ X ] Checked the cask is submitted to the correct repo.

Cask style fails with this warning I'm not sure how to resolve:

C:  5:  3: Cask/HomepageMatchesUrl: Github does not match github.com/zaquestion/lab/releases/download/v

However the hompage is hosted on github pages and everything else has been thoroughly tested.

[commitay]

Rejected Casks
The app is both open-source and CLI-only (i.e. it only uses the binary artifact). In that case, and in the spirit of deduplication, submit it first to Homebrew/core. If it is rejected there, you may then try again in Homebrew-Cask (link us to the issue on Homebrew so we can see their reasoning for rejection).