Automatic Generation of Isoclines

[nsmoker]

See Economic Dynamics in Discrete Time, Pg. 21

[nsmoker]

• [ ] Change from n to discretize, default should be ?? (NULL means get from dsrange, but should we have a good default first? If we know n=200 tends to work pretty well.... maybe NULL should mean 'n=200?)
• [ ] Have different x and y discretizations as an option
• [ ] Investigate why n=100 fails on the vertical line (horizontal makes sense)
• [ ] add an option to only create the x or y isocline
• [ ] Add "points" and change dscurve to also use "points=True" instead of discretize
• [ ] Let dsintersctions just take a simsicolines directly.
• [ ] Avoid regenerating the ranges and y points for the two isoclines (meh, do we really care?) (this would be done by saving them as attributes of the object)

[sfogarty]

Instead, use an epsilon in velocity coloring to make a black border.