Adding class to the_post_thumbnail()

[Tabrisrp]

Hello,

By default, the_post_thumbnail can have an array parameter passed to it, with (among other) the class to add to the html generated code. With WPThumb we can't do it anymore, but I think it could be useful.

[willmot]

Makes sense. Pull Requests welcome :-)

[joehoyle]

This should already work, so perhaps we broke something

[crixlet]

I found that i needed to add a space before the class in the wp_thumb post thumbnail array in order to get it to work ('class' => ' img-responsive')