Improve visualizations.

[rcjackson]

Visualization of wind fields is a difficult task. While in PyDDA we have strived to provide a quality visualization module using standard markers such as wind barbs, stream lines, and quiver plots, there are still difficulties that arise in effectively visualizing winds. We are interested in any pull requests that help us improve our visualization module, whether that would be simply the modification of current techniques to better adapt to a given dataset, or entirely new ways of visualizing winds.