Don't use (interactive "r")

This caused the fn to fail in a fresh emacs where mark was unset.  Using
region-active-p with region-beginning and region-end seems like the way
to go.
Remove uneeded code after cljr--add-ns-prefix change
Add basic test and make it pass

- Removed require-final-newline as it doesn't seem to impact the test.
- For the tests to pass I had to use (open-line 2) instead of 1, when
  appending to the destination buffer.  This results in two lines
  between defns when I try it locally, even with emacs -Q.  I have no
  idea what this is about.
Be smarter about modifying the ns when moving defns

Obviously easier to update the existing :require clause than to rebuild
it.  Don't code when tired, kids.
Change order of names in :refer clause created by move-forms refactoring

These now match the order they appear in the the buffer.
Tests with visual selection