Ip location

I was wondering why calling map.locate did not work for me.
After some research I found out, that it had to do with HTML5 geolocation, which is not supported on my browser.
So I implemented a fallback to ip based location (inspired by this https://github.com/onury/geolocator)

I really think that this would improve leaflet a bit... please tell me what you think about it :-)