add `npm view .`

Fixes #5520

This adds back the ability to run `npm view .`. If a package.json
exists in the cwd, it reads it to get the name and author. It fetches
the package from the registry. If the local package.json has an author
field, it validates that the author of the local package matches the
author of the fetched package.

Includes multiple tests for `npm view`
Just do `var dir = npm.prefix`.  Also, should not work when `npm.config.get("global")` is true.