DO NOT MERGE YET - .deb: Handle semver conversion when only one digit is present

Currently, if a gem has a semantic version requirement on a single digit number (aka "~> 3"), FPM winds up converting this into (in debian, at least) ">= 3" and "<< 0", which is obviously not satisfiable. The fix is fairly straightforward, but there is a test I've not yet figured out how to satisfy.