Pass along the Version object instead of string

- Turning the versions into strings causes issues when we go from
something like 9 to 10, since it's a lexicographic comparison
- the Version object from the Changelog module implements __cmp__, so
it's directly comparable
- Pass around Version objects, and only stringify them when needed

Change-Id: I9f15d8e7f51a85ca7e79018360c6d2f79af7b74e
1 file changed