Update dev file

Separated out from #63 

Dev.php is just a helper file for development - It shouldn't normally be included - it just includes a single shortcode with all the different fields. I think its useful for anyone wanting to get started with shortcake.

Problem is - we have a 'pullquote' shortcode on Fusion - and they conflict.

This updates to make it a bit more generic and better for testing.

@danielbachhuber review & merge