Fix in page nav width bug

Fix bug with long text in in-page nav items: the text flow outside the width
of the container when fixed position on wide screens. Fixed by copying the
width from the container.

src/components/in-page-nav/in-page-nav.js

@@ -215,8 +215,10 @@ export default class InPageNav {
 				// Move element to the target
 				this.$inpagenav.appendTo(this.$wideTarget);
 			}
+			this.$inpagenav.width(this.$wideTarget.width());
 		} else if(!this.$inpagenav.parent().is(this.$el)) {
 			this.$inpagenav.appendTo(this.$el);
+			this.$inpagenav.width("auto");
 		}
 	}