Simpler default syntax for markdown attributes.

- on slides: .slide x=y
- on elements: .element x=y

Those are detected in html comment, in order to not be visible
if a markdown is edited in an html editor.

plugin/markdown/markdown.js

@@ -28,8 +28,8 @@
 
 	var DEFAULT_SLIDE_SEPARATOR = '^\n---\n$',
 		DEFAULT_NOTES_SEPARATOR = 'note:',
-		DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR = '{\\\.\s*?([^}]+?)}',
-		DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR = 'slide-attributes:\\\s(.*?)$';
+		DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR = '\\\.element\\\s*?(.+?)$',
+		DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR = '\\\.slide:\\\s*?(\\\S.+?)$';
 
 
 	/**