Have the prelude export minimum and maximum at more general types.
Have the prelude export product at a more general type.
Merge pull request #33 from dmcclean/folds

Generalized types for commonly convenient folds
Remove (^+) operator.
Port to NumType 0.4.
Added degree fahrenheit.
Merge pull request #35 from dmcclean/fahrenheit

Added degree fahrenheit.
Merge in changes from master.