Update Goreleaser and build for more architectures

[frankywahl]

This allows for compatibility with new version of goreleaser.

It also adds universal binaries and support for more architectures

I would also propose releasing a brew formula, by adding something like:

brews:
  - name: mfaws
    folder: Formula
    description: Handling AWS CLI with Multi Factor Authentication
    homepage: https://github.com/pbar1/mfaws
    repository:
      owner: frankywahl
      name: homebrew-tap
    test: |
      assert_match "{{ .Version }}, commit {{ .ShortCommit }}, built at {{ .Date }}", shell_output("#{bin}/mfaws version")
    # ...

It would make it an easy way to have many users install the CLI quickly.

For the time being - I've done my own here but having something automated and up to date with all architectures would be nice.