move dependencies to vendor

vendor/github.com/docker/libcompose/lookup/simple_env.go

@@ -0,0 +1,24 @@
+package lookup
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/docker/libcompose/project"
+)
+
+// OsEnvLookup is a "bare" structure that implements the project.EnvironmentLookup interface
+type OsEnvLookup struct {
+}
+
+// Lookup creates a string slice of string containing a "docker-friendly" environment string
+// in the form of 'key=value'. It gets environment values using os.Getenv.
+// If the os environment variable does not exists, the slice is empty. serviceName and config
+// are not used at all in this implementation.
+func (o *OsEnvLookup) Lookup(key, serviceName string, config *project.ServiceConfig) []string {
+	ret := os.Getenv(key)
+	if ret == "" {
+		return []string{}
+	}
+	return []string{fmt.Sprintf("%s=%s", key, ret)}
+}