Use colors in `inspect`

* Added a simple wrapper around the standard `util.inspect` function (with `{colors:true}` set by default), named `docpadUtil.inspect` (found in `src/lib/util`)
* (In `src/lib`) Changed calls to `util.inspect` to `docpadUtil.inspect`
* Now, when the user types `docpad info`, their config info is much more readable! ☺