Fix for #535:

- hide/show code editor based on markdown editor state (could be CODE or PREVIEW);
- changed styles for code editor;

browser/components/MarkdownEditor.js

@@ -221,7 +221,10 @@ class MarkdownEditor extends React.Component {
         onKeyDown={(e) => this.handleKeyDown(e)}
         onKeyUp={(e) => this.handleKeyUp(e)}
       >
-        <CodeEditor styleName='codeEditor'
+        <CodeEditor styleName={this.state.status === 'CODE'
+            ? 'codeEditor'
+            : 'codeEditor--hide'
+          }
           ref='code'
           mode='GitHub Flavored Markdown'
           value={value}

browser/components/MarkdownEditor.styl

@@ -4,8 +4,14 @@
 .codeEditor
   absolute top bottom left right
 
+.hide
+  z-index 0
+  opacity 0
+  pointer-events none
+
 .codeEditor--hide
   @extend .codeEditor
+  @extend .hide
 
 .preview
   display block
@@ -17,7 +23,5 @@
 
 .preview--hide
   @extend .preview
-  z-index 0
-  opacity 0
-  pointer-events none
+  @extend .hide