Add AsyncStringFeatureParser and use plain

XMLHttpRequest in the KML example

Since the content-type on github.io is application/octet-stream we need
to implement an Async string based parser interface in the KML parser.
Also use plain XmlHttpRequest in the example instead of jQuery Ajax since
the vector-features example also uses that.

examples/kml.html

@@ -48,7 +48,6 @@
 
     </div>
 
-    <script src="jquery.min.js" type="text/javascript"></script>
     <script src="loader.js?id=kml" type="text/javascript"></script>
     <script src="../resources/social-links.js" type="text/javascript"></script>