refactor(manager): command pulling to command pushing and tests

manager/util.go

@@ -0,0 +1,13 @@
+package manager
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+)
+
+func postJSON(url string, obj interface{}) (*http.Response, error) {
+	b := new(bytes.Buffer)
+	json.NewEncoder(b).Encode(obj)
+	return http.Post(url, "application/json; charset=utf-8", b)
+}