Add information about Glade UI and Poppler

Hi, very interesting software proposition.  I heard about it yesterday and I'm currently testing it.  Anyway, during the installation phase, I got some warning during the installation. Don't know if it's useful.  See my log (https://ezcrypt.it/wnAn#x8MMoVqNGkwj7MAoyMhJg1Ne) and the pull request.  Feel free to reject it if you think it's not so useful.