Markdown: Tables does not work

When user tries to add table, he can't do it

Pre-condition:

1. User is logged in
2. Create article form is opened
   Steps to reproduce:
3. Insert table from Markdown syntax reference

   | Tables        | Are           | Cool  |
   | ------------- |:-------------:| -----:|
   | col 3 is      | right-aligned | $1600 |
   | col 2 is      | centered      |   $12 |
   | zebra stripes | are neat      |    $1 |
   
   Markdown | Less | Pretty
   --- | --- | ---
   *Still* | `renders` | **nicely**
   1 | 2 | 3
   

   Actual result: All text is displayed as plain text
   Expected result: tables are displayed