Add markdown format support (#25)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

node_modules/showdown/test/ghost/markdown-magic.md

@@ -0,0 +1,43 @@
+### Automatic Links
+
+```
+https://ghost.org
+```
+
+https://ghost.org
+
+### Markdown Footnotes
+
+```
+The quick brown fox[^1] jumped over the lazy dog[^2].
+
+[^1]: Foxes are red
+[^2]: Dogs are usually not red
+```
+
+The quick brown fox[^1] jumped over the lazy dog[^2].
+
+
+### Syntax Highlighting
+
+    ```language-javascript
+       [...]
+    ```
+
+Combined with [Prism.js](http://prismjs.com/) in the Ghost theme:
+
+```language-javascript
+// # Notifications API
+// RESTful API for creating notifications
+var Promise            = require('bluebird'),
+    _                  = require('lodash'),
+    canThis            = require('../permissions').canThis,
+    errors             = require('../errors'),
+    utils              = require('./utils'),
+
+    // Holds the persistent notifications
+    notificationsStore = [],
+    // Holds the last used id
+    notificationCounter = 0,
+    notifications;
+```