Remove unused simplejson dependency
Remove unused simplejson dependency

It's not used anywhere and it gets in the way of packaging.

gi11es/thumbor,abaldwin1/thumbor,abaldwin1/thumbor,davduran/thumbor,fanhero/thumbor,thumbor/thumbor,scorphus/thumbor,Bladrak/thumbor,fanhero/thumbor,thumbor/thumbor,okor/thumbor,abaldwin1/thumbor,abaldwin1/thumbor,marcelometal/thumbor,voxmedia/thumbor,kkopachev/thumbor,gi11es/thumbor,kkopachev/thumbor,davduran/thumbor,thumbor/thumbor,fanhero/thumbor,marcelometal/thumbor,voxmedia/thumbor,Bladrak/thumbor,okor/thumbor,okor/thumbor,davduran/thumbor,gi11es/thumbor,scorphus/thumbor,davduran/thumbor,kkopachev/thumbor,marcelometal/thumbor,scorphus/thumbor,fanhero/thumbor,kkopachev/thumbor,scorphus/thumbor,voxmedia/thumbor,thumbor/thumbor