pragma/import cleanup
depend on NumInstances 1.2 and import only Data.NumInstances.Tuple

Fixes #48.  Now we only export the Num (and Eq and Show) instances for
tuples.  Anyone wishing to use Diagrams.CubicSpline with a vector
space built over functions can import Data.NumInstances.Function themselves.
ignore .diagrams-cache
change Data.NumInstances import in Diagrams.TwoD.Types (see #48)