Check Documentation Code Blocks

[GeeH]

Check code blocks are correct

TLDR; Check in all files that codeblocks are correct, in PSR-2 format and have PHP syntax highlighting applied.

Code blocks should be in the following format...

```php
 'ZEND-FRAMEWORK');

// No required options
$rendererOptions = array();
$renderer = Barcode::factory(
    'code39', 'image', $barcodeOptions, $rendererOptions
);

```

Note the three backticks then php in the opening fence, and the closing fence is just three backticks. It's common for the opening backticks to have no code type, or something like source.

Code should also have been automatically formatted into PSR-2 format, but sometimes these slip through the net.

[weierophinney]

Fixed with #15.