v2.0.0

• Switch to version hooks. Fixes #25.

  Using version-name and version-origin instead of the which
  supports more nodenv commands, includeing nodenv version.

  Full explanations of hooks here:
  https://github.com/rbenv/rbenv/wiki/Authoring-plugins#rbenv-hooks

• Extract plugin_root script

  To enable moving shared functions into libexec.

• Reorganize functions in libexec

  Prompted by the need to share precedence checks betweeen version-name
  and version-origin, I've extracted mosted of the package-json-engine
  logic into functions in libexec.

  Also fixes #10.

• Rebase nodenv-shell precedence onto version support

  With a slightly different check for nodenv shell that lets us still
  respect shell version even when it matches the global version.

• Lint with Shellcheck

  And run automatically on travis