Support multicell selection in markdown conversion

Fixes #803

(c) Copyright IBM Corp. 2015

notebook/static/notebook/js/actions.js

@@ -254,7 +254,7 @@ define(function(require){
             help    : 'to markdown',
             help_index : 'cb',
             handler : function (env) {
-                env.notebook.to_markdown();
+                env.notebook.cells_to_markdown();
             }
         },
         'change-cell-to-raw' : {

notebook/static/notebook/js/maintoolbar.js

@@ -111,7 +111,7 @@ define([
                 that.notebook.cells_to_code();
                 break;
             case 'markdown':
-                that.notebook.to_markdown();
+                that.notebook.cells_to_markdown();
                 break;
             case 'raw':
                 that.notebook.cells_to_raw();

notebook/static/notebook/js/notebook.js

@@ -1191,6 +1191,7 @@ define(function (require) {
             this.to_code(indices[i]);
         }
     };
+
     /**
      * Turn a cell into a code cell.
      * 
@@ -1222,6 +1223,21 @@ define(function (require) {
         }
     };
 
+    /**
+     * Turn one or more cells into Markdown.
+     *
+     * @param {Array} indices - cell indices to convert
+     */
+     Notebook.prototype.cells_to_markdown = function (indices) {
+        if (indices === undefined) {
+            indices = this.get_selected_cells_indices();
+        }
+
+        for(var i=0; i < indices.length; i++) {
+            this.to_markdown(indices[i]);
+        }
+     };
+
     /**
      * Turn a cell into a Markdown cell.
      *