Function to plot co-ordinates from a file on a map

Code to load co-ordinate data from a file and call function to plot co-ordinates on a map. The input file is assumed to have co-ordinates (longitude and latitude). Has example code to load open data, take a snapshot and plot it on a map for USA.
Adapted from code by user Amro in stackoverflow - http://stackoverflow.com/questions/24707299/matlab-mapping-toolbox-how-to-plot-lat-lon-coordinates-onto-a-created-map
Works for USA only.