Changes in version 0.1-2                        

  - the default behoviour to plot towns with fixed size

  - a new argument towns, can be either a boolean or a character
    indicating the variable to map with the size of the points
    (currently only "pop")

  - a new size argument, length one for a fixed size and lenght two to
    define the range of the sizes of the points

  - a new shape argument, length one to define the shape of the points
    or length two to map the shape with the capital

  - new oceans and background argument to set the colour of the oceans
    and of the background