Publish new version in homebrew tap whenever there is a new release

[hangxie]

Right now homebrew tap is a separated repo and it was always triggered manually to publish a new version, as I want to have a manual test before it may affect others.

However, there was never an issue in the past a year or two (touch the wood), so I think it's pretty safe to publish new version in homebrew tap when there is a new release here.