Fix bug where tweak loses integer mode

Fix issue with integer value stepper becoming a real value stepper after the first update.
The value type of a UIStepper is double, so when boxing this into an NSNumber,
the mode needs to be considered to ensure the updated tweak remains an integer value.
2 spaces for indentation rather than tabs
Merge pull request #37 from hverlind/hverlind/master

Fix bug where tweak loses integer mode