yq: new package

[teaguesterling]

This adds a basic package for yq, a go-based CLI tool for querying yaml files similar to jq.

[teaguesterling]

@spackbot fix styles

[spackbot-app]

Let me see if I can fix that for you!

[spackbot-app]

I was able to run spack style --fix for you!

spack style --fix

==> Running style checks on spack
  selected: isort, black, flake8, mypy
==> Modified files
  var/spack/repos/builtin/packages/yq/package.py
==> Running isort checks
  isort checks were clean
==> Running black checks
reformatted var/spack/repos/builtin/packages/yq/package.py
All done! ✨ 🍰 ✨
1 file reformatted.
  black checks were clean
==> Running flake8 checks
  flake8 checks were clean
==> Running mypy checks
lib/spack/spack/version/version_types.py:145: error: Argument 2 to "StandardVersion" has incompatible type "*Tuple[Tuple[Any, ...], Tuple[Any, ...]]"; expected "Tuple[Tuple[Any, ...], Tuple[Any, ...]]"  [arg-type]
lib/spack/spack/version/version_types.py:452: error: Argument 2 to "StandardVersion" has incompatible type "*Tuple[Tuple[Any, ...], Tuple[Any, ...]]"; expected "Tuple[Tuple[Any, ...], Tuple[Any, ...]]"  [arg-type]
lib/spack/spack/version/version_types.py:481: error: Argument 2 to "StandardVersion" has incompatible type "*Tuple[Tuple[Any, ...], Tuple[Any, ...]]"; expected "Tuple[Tuple[Any, ...], Tuple[Any, ...]]"  [arg-type]
Found 3 errors in 1 file (checked 625 source files)
  mypy found errors

Keep in mind that I cannot fix your flake8 or mypy errors, so if you have any you'll need to fix them and update the pull request. If I was able to push to your branch, if you make further changes you will need to pull from your updated branch before pushing again.

I've updated the branch with style fixes.