Markers can now be given edge and face colors as numpy arrays.
Marker constructor checks if the specified colors are numpy arrays, and if so, uses a ColorArray instead of a Color.
Improvement based on @Eric89GXL's code review.
Fix for docstrings to use standard formatting.
The colors in the markers demo now interpolate from green to red for each marker individually.
Adding border_width parameter to certain PolygonVisuals, the default was =1 but it's sometimes set to =2.  Where are the .png files stored?
Merge pull request #636 from alexjc/marker-colors

MarkersVisual supports unique marker colors for edges/faces passed as numpy array.