Added module to graph for the plotting of grid data on a map. Updated init with a conditional import if pyproj and basemap exists
Bug squash
Added an example for the map based plotting of pyart grid objects
Added an example for the map based plotting of pyart grid objects
added example output from the mapping example
Bug Squash
Merge branch 'scollis/master' into from_pr_67
WIP: fixing up grid_plotting
MAINT: refactor of GridMapDisplay
DOC: documentation for GridMapDisplay object
TST: unit tests and framework for graph/gridmapdisplay
DOC: documentation for testing modules
Merge branch 'from_pr_67'

Conflicts:
	pyart/graph/__init__.py