chore(lodash): require specific lodash/assign module

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ### vNEXT
+- Require specific lodash/assign module instead of entire package, so memory impact is reduced [PR #196](https://github.com/apollographql/subscriptions-transport-ws/pull/196)
 
 ### 0.7.3
 - Fix for first subscription is never unsubscribed [PR #179](https://github.com/apollographql/subscriptions-transport-ws/pull/179)

src/helpers.ts

@@ -1,5 +1,5 @@
 import { SubscriptionClient } from './client';
-import { assign } from 'lodash';
+import assign = require('lodash.assign');
 
 /**
  * @deprecated This method will become deprecated in the new package graphql-transport-ws.

typings.d.ts

@@ -2,6 +2,11 @@ interface Array<T> {
   indexOfField : (propertyName: string, value: any) => number;
 }
 
+declare module 'lodash.assign' {
+  import {assign} from 'lodash';
+  export = assign;
+}
+
 declare module 'lodash.isobject' {
   import {isObject} from 'lodash';
   export = isObject;