added milestone lines to gantt chart

modified the constructor to accept milestone dates and added a function
which draws a line on each milestone date. also removed the whitspaces
at the the end of a line which was actually just an accident, but i
think it is also useful because of saving bytes :-)
Add milestone labels

Usage:
```PHP
$gantt = new Gantti($data, array(
	'title'      => 'CMS'.$info["cms"],
	'cellwidth'  => 25,
	'cellheight' => 35,
	//'milestones' => array($oed, $ted)
	'milestones' => array(
		array(
			'date' => "2013-12-24",
			'label' => "Today"
		)
	)
));
```
Add titles for labels

"Further description" for labels
Merge pull request #1 from n7st/master

Taking n7st