Merge pull request #1033 from jcb91/freeze

[freeze] fix typo/inconsitent state naming

Author: jcb91

src/jupyter_contrib_nbextensions/nbextensions/freeze/main.js

@@ -100,6 +100,7 @@ define([
                 bg = "";
                 break;
             case 'read_only':
+            case 'readonly':
                 cell.metadata.editable = false;
                 cell.metadata.deletable = false;
                 if (cell.metadata.run_control !== undefined) {