Avoid false positives versionCheck when versionScheme != early-semver

[bjaglin]

sbt-version-policy/sbt-version-policy/src/main/scala/sbtversionpolicy/Compatibility.scala

Lines 63 to 85 in 323d010

	/**
	* Validates that the given new `version` matches the claimed `compatibility` level.
	* @return Some validation error, or None if the version is valid.
	*/
	def isValidVersion(compatibility: Compatibility, version: String): Boolean = {
	val versionNumber = VersionNumber(version)
	val major = versionNumber._1
	val minor = versionNumber._2
	val patch = versionNumber._3
	compatibility match {
	case Compatibility.None =>
	// No compatibility is guaranteed: the major version must be incremented (or the minor version, if major is 0)
	if (major.contains(0)) patch.contains(0) // minor version bump
	else minor.contains(0) && patch.contains(0) // major version bump
	case Compatibility.BinaryCompatible =>
	// No source compatibility is guaranteed, the minor version must be incremented (or the patch version, if major is 0)
	if (major.contains(0)) true // always OK
	else patch.contains(0) // minor version bump
	case Compatibility.BinaryAndSourceCompatible =>
	// OK, the version can be set to whatever
	true
	}
	}

assumes the module being checked is early-semver as of v2.0.1.

It should either support other versionSchemes or fail if it's not early-semver.

[julienrf]

Related discussion #60.