[RPM] replace dashes (-) with tildes (~) in version

RPM 4.10+ added support for using the tilde (~) as a way to mark versions as lower priority in comparisons. More details on this feature can be found here:

  http://rpm.org/ticket/56

Replacing dashes with tildes will ensure pre-release versions (e.g. 12.0.0-rc.1) get sorted before final versions (e.g. 12.0.0).

/cc @opscode/release-engineers