Comment installer MapData

mapdata.py can be installed from PyPI with pip, using the command:

    pip install mapdata

Alternatively, it can be downloaded from the release page on OSDN.  If this approach is taken, its dependencies will also have to be installed.  Dependencies are tkinter, tkintermapview, pyproj if geographic coordinates will have to be transformed to decimal degrees in WGS84, and odfpy if a table of selected data will be exported to an OpenDocument spreadsheet.  All of these libraries can be installed from PyPI.