Better README

Makefile

@@ -24,7 +24,7 @@ update:
 .PHONY: update
 
 release:
-	@if [[ ! "${v}" =~ ^[0-9]+\.[0-9]+\.[0-9]+-[0-9]+.*$$ ]]; then echo "Usage: make release V=X.X.X-Y"; exit 1; fi
+	@if [[ ! "${v}" =~ ^[0-9]+\.[0-9]+\.[0-9]+-[0-9]+.*$$ ]]; then echo "Usage: make release v=X.X.X-Y"; exit 1; fi
 	git tag v${v}
 	git push origin v${v}
 .PHONY: release