scroll overflow-x on rendered markdown

treat markdown the same as output

IPython/html/static/notebook/less/textcell.less

@@ -35,6 +35,10 b' h1,h2,h3,h4,h5,h6 {'
     display: none;
 }
 
+.text_cell.rendered .rendered_html {
+    overflow-x: auto;
+}
+
 .text_cell.unrendered .text_cell_render {
     display:none;
 }

IPython/html/static/style/ipython.min.css

@@ -1184,6 +1184,9 b' h6:hover .anchor-link {'
 .text_cell.rendered .input_area {
   display: none;
 }
+.text_cell.rendered .rendered_html {
+  overflow-x: auto;
+}
 .text_cell.unrendered .text_cell_render {
   display: none;
 }

IPython/html/static/style/style.min.css

@@ -9976,6 +9976,9 b' h6:hover .anchor-link {'
 .text_cell.rendered .input_area {
   display: none;
 }
+.text_cell.rendered .rendered_html {
+  overflow-x: auto;
+}
 .text_cell.unrendered .text_cell_render {
   display: none;
 }