Added meta field description as field_description

[sixlive]

I have never contributed to a GIT project before so bear with me if this pull request isn't done right.

I tried to keep the usage as easy as possible.

Usage:

$tests->add_meta_box( array(
    'id' => 'test-box',
    'context' => 'normal',
    'fields' => array(
        'test-field-one' => array('type'=>'text', 'field_description'=> 'Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor. Sed posuere consectetur est at lobortis. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.'),
        'test-field-two' => array('type'=>'media', 'field_description'=> 'Aenean lacinia bibendum nulla sed consectetur. Sed posuere consectetur est at lobortis.')
    )
) );

Renders:

[ebillias]

Nice, just what I was looking for :)

[sixlive]

Awesome :)

[mboynes]

Hey @sixlive, sorry for the delay here and thanks for the pull request! I want to give this some thought before adding the description, because I'd like to make sure it's plenty flexible. I think it's definitely worth adding, so thanks!

[sixlive]

@mboynes no worries! so far I've found it super flexible, we have used it on ~8 sites at our firm!

[louy]

@mboynes any updates regarding this?