Remove metadata spellcheck support

public/docs/yaml-metadata.md

@@ -116,15 +116,3 @@ This option let you to choose to parse mathjax syntax or not.
 ```xml
 mathjax: false
 ```
-
-spellcheck
----
-**Warning: Experimental feature!**
-This option let you to choose to enable spell checking feature or not.
-
-> default: not set (which will be false)
-
-**Example**
-```xml
-spellcheck: true
-```

public/js/extra.js

@@ -102,13 +102,11 @@ function parseMeta(md, edit, view, toc, tocAffix) {
     var lang = null;
     var dir = null;
     var breaks = true;
-    var spellcheck = false;
     if (md && md.meta) {
         var meta = md.meta;
         lang = meta.lang;
         dir = meta.dir;
         breaks = meta.breaks;
-        spellcheck = meta.spellcheck;
     }
     //text language
     if (lang && typeof lang == "string") {
@@ -140,18 +138,6 @@ function parseMeta(md, edit, view, toc, tocAffix) {
     } else {
         md.options.breaks = true;
     }
-    // spell check
-    if (typeof editor === 'object') {
-        var mode = null;
-        if (typeof spellcheck === 'boolean' && spellcheck) {
-            mode = 'spell-checker';
-        } else {
-            mode = 'gfm';
-        }
-        if (mode && mode !== editor.getOption('mode')) {
-            editor.setOption('mode', mode);
-        }
-    }
 }
 
 var viewAjaxCallback = null;