Make skew-T special lines more automatic

[dopplershift]

It would be good for the special lines, especially the adiabats, to be more dynamic and properly respond to the plot bounds.

Ideally, these should be handled like gridlines. We would need to interpolate a line in plot coordinates [0, 1] and then do the proper transform and calculation to produce the adiabats. My only concern would be performance.

[dopplershift]

Another option would be to add an event handler listening for viewlim events and resetting the data for the special lines.

[dopplershift]

There may be a class in matplotlib that helps:

from mpl_toolkits.axisartist.grid_helper_curvelinear import GridHelperCurveLinear

Not sure if it's good idea or not to use this, but it might at least point the way.

[dopplershift]

To be more explicit, here is an example from Matplotlib's gallery showing how to use this stuff.

Might also be useful (as in the example) to better do Hodograph as the "polar but in a rectangular axes" shows.