The content of holocron example post is improved

This commit changes the text of holocron.mdown file, adding info about holocron
features and its basic usage.

Fixed #16
The code block is highlighter with errors:

 ![](http://i.imgur.com/QcVRPim.png)

since we don't specify a languge to highlight and the script was try to auto-detect it.

So I propose to specify a language to highlight (`bash`):

    ```bash
    $ holocron init
    # => Generates initial simplified configuration file and this blog post as example
    
    $ holocron build
    # => Builds html entries from the markdown sources and runs generators for additional content
    
    $ holocron serve
    # => Runs a development server at http://localhost:8000/
    ```

which is leads to the result:

![](http://i.imgur.com/MCHhEUS.png)