Changed Popup Type from "Framed" to Anchored and added an anchor to fix
the popup on it's position, even after zooming.
Added standard close-function to the close-button of bootstrap.
Added additional function for close-callback.
updated close function to call hide of OpenLayers.PopUp
Fix for the Position on zooming
Added example-code line to add popup to the map
Merge pull request #5 from Schlangguru/master

Fix for positioning and close