fixes markdown issues on home page

the Markdown function wasn't doing anything in the home page section of the `/dropplets/index.php`, however, if you wrap the intro text with the Markdown function in the get_all_posts function lower down, the Markdown is interpretted correctly. Removed the Markdown wrapper from $content and added it to $fcontents[4] in get_all_posts() 

updates /template/posts.php to fix empty `<p></p>` tags which result from this change, and makes the intro get indented via the basic css `p + p` rules. Removed the `<p>` tags from `/template/posts.php` since the `<p>` tags are being added by the Markdown anyway.

fixes https://github.com/circa75/dropplets/issues/9