Upgrade to CodeMirror v3.13

From v3.12

CodeMirror-3.13/lib/codemirror.css

@@ -19,7 +19,7 @@
   padding: 0 4px; /* Horizontal padding of content */
 }
 
-.CodeMirror-scrollbar-filler {
+.CodeMirror-scrollbar-filler, .CodeMirror-gutter-filler {
   background-color: white; /* The little square between H and V scrollbars */
 }
 
@@ -28,6 +28,7 @@
 .CodeMirror-gutters {
   border-right: 1px solid #ddd;
   background-color: #f7f7f7;
+  white-space: nowrap;
 }
 .CodeMirror-linenumbers {}
 .CodeMirror-linenumber {
@@ -124,7 +125,7 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
 /* The fake, visible scrollbars. Used to force redraw during scrolling
    before actuall scrolling happens, thus preventing shaking and
    flickering artifacts. */
-.CodeMirror-vscrollbar, .CodeMirror-hscrollbar, .CodeMirror-scrollbar-filler {
+.CodeMirror-vscrollbar, .CodeMirror-hscrollbar, .CodeMirror-scrollbar-filler, .CodeMirror-gutter-filler {
   position: absolute;
   z-index: 6;
   display: none;
@@ -141,16 +142,18 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
 }
 .CodeMirror-scrollbar-filler {
   right: 0; bottom: 0;
-  z-index: 6;
+}
+.CodeMirror-gutter-filler {
+  left: 0; bottom: 0;
 }
 
 .CodeMirror-gutters {
   position: absolute; left: 0; top: 0;
-  height: 100%;
   padding-bottom: 30px;
   z-index: 3;
 }
 .CodeMirror-gutter {
+  white-space: normal;
   height: 100%;
   padding-bottom: 30px;
   margin-bottom: -32px;