fix docker-compose version

Production/docker-compose.btc-ltc.yml

@@ -1,4 +1,4 @@
-version: 3
+version: "3"
 services:
   nginx:
     restart: always

Production/docker-compose.btc.yml

@@ -1,4 +1,4 @@
-version: 3
+version: "3"
 services:
   nginx:
     restart: always

Production/docker-compose.yml

@@ -1,4 +1,4 @@
-version: 3
+version: "3"
 services:
   nginx:
     restart: always

docker-compose-generator/src/DockerComposeDefinition.cs

@@ -61,7 +61,7 @@ namespace DockerGenerator
 
 			
 			YamlMappingNode output = new YamlMappingNode();
-			output.Add("version", new YamlScalarNode("3"));
+			output.Add("version", new YamlScalarNode("3") { Style = YamlDotNet.Core.ScalarStyle.DoubleQuoted });
 			output.Add("services", new YamlMappingNode(Merge(services)));
 			output.Add("volumes", new YamlMappingNode(volumes));
 			var result = serializer.Serialize(output);