Allow closing multiple functions to decrease indent level

Fixes #33.
Support for nested arrays in indentation rules

For instance:

```
<?php
$array = array(
    "foo" => "bar",
    42    => 24,
    "multi" => array(
         "dimensional" => array(
             "array" => "foo"
         )
    )
);
```
Improve support for nowdocs

Nowdocs can now contain syntax highlighting for supported languages, fixes #31.

Also add support for double-quoted identifiers in regular heredocs.