Add Tree tool (and other changes)

This was originally intended to just add the Tree functionality, but it turned into much more than that. 

I've gone through and cleaned things up to my liking (perhaps a bit too opinionated) so if you'd like me to revert anything back let me know. 

Example tree output:

```
$ php examples/tree.php 
ASCII:
|-Array
| |-Array
| | \-This is a 3rd layer
| \-This is a 2nd layer
\-Array
  \-Array
    |-This is also cool
    |-This is even cooler
    \-Array
      |-Awesome eh?
      \-Array
        \-Yep!

Markdown:
- Test
    - Something Cool
        - This is a 3rd layer
    - This is a 2nd layer
- Other test
    - This is awesome
        - This is also cool
        - This is even cooler
        - Wow like what is this
            - Awesome eh?
            - Totally
                - Yep!
```