Replace iFrame alerts with divs
parse HTML and convert to text

Closes https://www.pivotaltracker.com/story/show/76515360
Closes #94

LGTM given by: @hampei

Squashed commit of the following:

commit 5503d6154612c2cecce37da38d0efaf374062c4c
Author: Ivan Malykh <ivan@roqua.nl>
Date:   Mon Sep 8 16:59:49 2014 +0200

    make response_text to be an actual text

commit c2004033b1925d2d3208973df25e90361419827a
Author: Ivan Malykh <ivan@roqua.nl>
Date:   Mon Sep 8 16:11:52 2014 +0200

    reorder element generation and fix specs

commit b235340fd2f09882a87daa7c22556217acc43cb6
Author: Ivan Malykh <ivan@roqua.nl>
Date:   Mon Sep 8 12:29:20 2014 +0200

    append error_details div to errors div; remove iframe

commit c9f8a987581dd7b51d3ac8bc9a5b81d91e339929
Author: Ivan Malykh <ivan@roqua.nl>
Date:   Mon Sep 8 12:23:40 2014 +0200

    parse html and render text