Make version string compatible with Emacs < 24.4

`version-to-list` doesn't have snapshot support before 24.4. The `-cvs` suffix
is the closest we can get there and it will be interpreted as a snapshot version
on 24.4+ anyways.
Merge pull request #100 from bbatsov/version-fix

Make version string compatible with Emacs < 24.4
Try to use the more up-to-date snapshot packages

#99
Use cl-lib