Added functionality render sitemap.xml

Signed-off-by: Ilja <ilja@ilja-ThinkPad-W520.ctldomain.ad.local>
Switched to Pegdown Markdown processor from MarkdownJ
Allow date format used to be customised via configuration
Update Parser.java
Set default date format
Tweaked PR #66.
Merged #63.
Slightly modified PR #58.
Merged in #58
Fixes #55