added R script to read in JSON and put out .gif

The script reads in data from gemeentegeschiedenis.nl in JSON and then
makes an animation of it (it being the borders of the city of
Amersfoort for the past 2 centuries)
added resulting .gif of R-script reading in JSON

This gif images shows how the borders of the city of Amersfoort have
developed over the past 2 centuries (script used is rjson_tryout01.R