message: Remove mongoose promise override to allow for use of other promise libraries
diff: import 'reflect-metadata';
  import * as mongoose from 'mongoose';
  -(mongoose as any).Promise = global.Promise;
  -
  import { constructors, hooks, methods, models, plugins, schema, virtuals } from './data';
  export * from './method';
  @@ -109,7 +107,7 @@ export class Typegoose {
  if (getterSetters) {
  for (const key of Object.keys(getterSetters)) {
  if (getterSetters[key].options && getterSetters[key].options.overwrite) {
  - sch.virtual(key, getterSetters[key].options)
  + sch.virtual(key, getterSetters[key].options);
  } else {
  if (getterSetters[key].get) {
  sch.virtual(key, getterSetters[key].options).get(getterSetters[key].get);
  