Added helper for checking package versions

This is very helpful b/c it will check the NPM registry version (default behavior), but also the local and global versions of the package, and will print these versions if found.

Before:
```
→ npm v gulp version
3.8.5
```

After:
```
→ nvv gulp
NPM registry package: 3.8.5
Local package: 3.8.4
Global package: 3.8.5
```