Update getstations.js

It works like it should. It tries to get your position from your browser, and if that works gets the closest 20 stations (or locations which are tagged as stations). 

Things to do: 
Error messages for if location isn't supported or is denied by the browser, or if the request times out.
Instead of appending the results to a string, it should just leave them in an array.
The function, if successful, should call the placeid function, when that is done.
Looking up your location should possibly be another function, so that the rest of the function can be called with different coordinates.