0.1.6

• Added default options to tile_layer (ozak 1ad2336)
• Introduce free scale for geo_json (Nikolay Koldunov 21e2757)
• Added Image Overlay. (andrewgiessel b625613)
• All popups can take a popup_width keyword to adjust the width in
  text/HTML (ocefpaf #157).
• CAVEAT! Backwards incompatibly change: the keyword width in popups is now
  popup_width to avoid confusion with map width.
• Simpler HTML repr (ocefpaf a343106)

Bug Fixes

• WMS layer (Martin Journois 610b42d)
• Stamentoner URL (ocefpaf 7003dc5)