Change __construct access to public.

Allows this method for outputting a form, which doesn't work if access is private
`$caldera = new \Caldera_Forms();`
`$form    = $caldera::render_form( $caldera_id );`
Merge pull request #34 from Shelob9/patch-1

Change __construct access to public.
Merge pull request #37 from Desertsnowman/1.1.4

1.1.4