Also, constant lines are now drawn over the data. I'm not sure this is appropriate either, but in the case of the NucTrans data, this definitely works better. Perhaps this concept needs to be abstracted a bit more, but for now, this will do.
Fixed handling of a specified date interval for the x-axis in TimeSeries. It turns out, the problem was the child get_x_values was not being called because I was calling the parent get_data_values( 'x' ) explicitly in Plot.py.
Generalized the data_max and data_min operations.
Fixed get_time_range method to properly return both end points.
Began adding support to Plot to support maximum x & y values, but this currently doesn't work as the axis labels don't get generated correctly with this method.
Fixed some bugs in TimeSeries, and re-wired the date-handling so it now uses integers for the x-axis. These may be converted back to date/time later, but not unless the datetime module can handle timedelta division correctly. Even the dateutil module doesn't handle this.