lots of important stuff (#1883)

* lots of important stuff

* Update Constants.js

src/rest/handlers/sequential.js

@@ -0,0 +1,16 @@
+module.exports = function sequential() {
+  if (this.busy || this.limited || this.queue.length === 0) return;
+  this.busy = true;
+  this.execute(this.queue.shift())
+    .then(() => {
+      this.busy = false;
+      this.handle();
+    })
+    .catch(({ timeout }) => {
+      this.client.setTimeout(() => {
+        this.reset();
+        this.busy = false;
+        this.handle();
+      }, timeout || (this.resetTime - Date.now() + this.timeDifference + this.client.options.restTimeOffset));
+    });
+};