Adds mem_limit support for conversion

This commit adds mem_limit support. Taking the value from
docker-compose.yaml and converting it to it's associative value in
Kubernetes artifacts.

Closes (half) of
https://github.com/kubernetes-incubator/kompose/issues/267

pkg/loader/compose/compose.go

@@ -64,7 +64,6 @@ func checkUnsupportedKey(composeProject *project.Project) []string {
 		"Ipc":           false,
 		"Logging":       false,
 		"MacAddress":    false,
-		"MemLimit":      false,
 		"MemSwapLimit":  false,
 		"NetworkMode":   false,
 		"Pid":           false,
@@ -366,6 +365,7 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 		serviceConfig.VolumesFrom = composeServiceConfig.VolumesFrom
 		serviceConfig.Stdin = composeServiceConfig.StdinOpen
 		serviceConfig.Tty = composeServiceConfig.Tty
+		serviceConfig.MemLimit = composeServiceConfig.MemLimit
 
 		komposeObject.ServiceConfigs[name] = serviceConfig
 	}