Fix object type in replaceObjectInFooAtIndex:withObject:

The generated .m files should use the object class in

- (void)replaceObjectInFoosAtIndex:(NSUInteger)idx withObject:(Foo*)value

rather than the collection class (eg - (void)replaceObjectInFoosAtIndex:(NSUInteger)idx withObject:(NSOrderedSet*)value)
Merge pull request #231 from jdelStrother/patch-1

[FIX] object type in `-replaceObjectInFooAtIndex:withObject:`. (Jonathan del Strother)