.subpage400_bg class

makes top image 400px tall, to be used in promotions/banners on survey
pages.
austinsurvey bbq promo

created new class to make 400px promo clickable.  NOTE: I couldn't make
/assets/images/global/placeholder.gif src work, so I just pasted in the
path of the image I wanted there and it rendered.
Merge branch 'dev'