fixed layout document body margin reset to zero to ensure user styles…

…heet doesn't set default 8px margin all around, see readium/readium-js-viewer#673 (comment)

js/views/one_page_view.js

@@ -377,6 +377,10 @@ var OnePageView = function (options, classes, enableBookStyleOverrides, reader)
                 _$epubBody = undefined;
             } else {
                 _$epubBody = $("body", _$epubHtml);
+
+                if (!_enableBookStyleOverrides) { // fixed layout
+                    _$epubBody.css("margin", "0"); // ensures 8px margin default user agent stylesheet is reset to zero
+                }
             }
 
             //_$epubHtml.css("overflow", "hidden");