Currently, `exportedDctors` returns only a [ProperName] with the names of the data constructors. This is no good if you want to know about the arguments of each constructor. This commit fixes the issue by changing the return type to [(ProperName, [Type])]. On a related note, I wonder if the documentation for `isExported` and `isDctorExported` should encourage you to use `exportedDecls` and `exportedDctors`, as these are 'higher level' versions of what is really the same function, which won't require you to pattern match (and therefore hopefully be safer and less likely to break because of updates).