added spec to test webrat's ability to recognize image buttons
added spec to test webrat's ability to recognize image buttons

jacksonfish/webrat,johnbintz/webrat,m3talsmith/webrat,irfanah/webrat,brynary/webrat,djanowski/webrat,djanowski/webrat,m3talsmith/webrat,jacksonfish/webrat,irfanah/webrat,brynary/webrat,irfanah/webrat,johnbintz/webrat