potential 0.3.0

fix

• add check on data input
• correct URLs
• use mapsf current mapsf functions
• simplify examples

potential 0.2.0

Minor changes

• Change longlat arg default to FALSE in create_matrix()
• Use mapsf instead of cartography in all examples
• Use mapiso instead of isoband
• In epquipotential “xcoords” and “ycoords” are not needed anymore