npm docs without project name uses package.json in current dir

## Summary

- Allow `npm docs .` or `npm docs` which will look for a `package.json` in the current working directory.
- Updated `npm docs` usage to include `npm docs .` invocation
- Corrects functionality that shows value of `.homepage` if available. Previously always opened npm package page. (i.e. `npm docs hapi`).
- Drops unused requires/imports.

## Updated Error Scenarios

#### Directory has no `package.json`

    % npm docs .

![](https://cloudup.com/cylnupOqtJa+)

#### Directory has a `package.json` file, but no `.name` property:

    % npm docs

![](https://cloudup.com/cQmbJeSxoul+)