Replace SimpleMDE with custom Markdown editor

assets/sass/_form.sass

@@ -49,11 +49,15 @@ textarea:focus
   box-shadow: 0 0 8px rgba(82, 168, 236, 0.6)
 
 textarea
+  padding: 3px
   border: 1px solid #ccc
   width: 400px
   max-width: 99%
   height: 200px
   font-family: sans-serif
+  font-size: size('normal')
+  @include placeholder
+    color: color('lighter')
 
 select
   font-size: 1.0em

assets/sass/_markdown_editor.sass

@@ -1,15 +1,19 @@
-.markdown-editor-container
-  max-width: 400px
+@import variables
 
-div
-  &.CodeMirror, &.CodeMirror-scroll
-    max-height: 250px
-    min-height: 200px
-
-.markdown-editor-small div
-  &.CodeMirror, &.CodeMirror-scroll
-    min-height: 100px
-    max-height: 180px
-
-.form-column div.CodeMirror
-  margin-bottom: 10px
+.text-editor
+  button
+    font-size: size('normal')
+    border: none
+    color: color('light')
+    background: transparent
+    &:hover
+      color: link-color('primary')
+      cursor: pointer
+  .text-editor-preview-area
+    border: 1px solid color('lighter')
+    width: 400px
+    height: 200px
+    overflow: auto
+  .text-editor-toolbar
+    button:first-child
+      padding-left: 0

assets/sass/_mixins.sass

@@ -31,8 +31,6 @@
 @mixin placeholder
   &::-webkit-input-placeholder
     @content
-  &:-moz-placeholder
-    @content
   &::-moz-placeholder
     @content
   &:-ms-input-placeholder