backtick -> backticks (revert)

lib/parser_inline.js

@@ -16,7 +16,7 @@ var _rules = [
   [ 'text',            require('./rules_inline/text') ],
   [ 'newline',         require('./rules_inline/newline') ],
   [ 'escape',          require('./rules_inline/escape') ],
-  [ 'backtick',        require('./rules_inline/backtick') ],
+  [ 'backticks',       require('./rules_inline/backticks') ],
   [ 'strikethrough',   require('./rules_inline/strikethrough') ],
   [ 'emphasis',        require('./rules_inline/emphasis') ],
   [ 'link',            require('./rules_inline/link') ],

lib/presets/commonmark.js

@@ -56,7 +56,7 @@ module.exports = {
     inline: {
       rules: [
         'autolink',
-        'backtick',
+        'backticks',
         'emphasis',
         'entity',
         'escape',