Match on the highest version number instead of direct equality checking

This commit fixes #36 as well as a few underlying issues thereof. Operating systems define their "named" platforms differently. For example, Ubuntu defines an OS release as X.Y (like Ubuntu 10.04 -> "precise"), whereas Debian defines an OS release as X (like Debian 7 -> "wheezy"). Prior to this commit, a new release of Debian (like 7.1) would fail to match on the `debian_wheezy?` matcher.