Allow wildcard and multi domain authHost option

As described in #185 as well as #135:
- allow for wildcard domain declaration in authHost option (e.g. authHost = '.myapp.com') so one can use the laravel-echo-server with a multi tenant/subdomain system 
- as well as a multi domain system, where different authentication servers are used. 
The currently appropriate authentication domain is retrived from the referer and matched with the (optional: wildcard) domain declaration from the authHost option as a whitelist (which can be either an array or a string). In case none is matched with the referer, the last one in the array is taken (in case of string, the only one). 
@tlaverdure @barryvdh please check. I have done my best to write this up in TS, but I don't have a compile system for this setup, so I have only tested it in vanilla JS and then afterwards added the TS specific types for this PR.
Thanks!

Author: tobiasvielmetter

src/channels/private-channel.ts

@@ -26,14 +26,8 @@ export class PrivateChannel {
      * @return {Promise<any>}
      */
     authenticate(socket: any, data: any): Promise<any> {
-        var authHost = this.authHost();
-        var referer = url.parse(socket.request.headers.referer);
-        
-        if(referer.hostname.substr(referer.hostname.indexOf('.'))===authHost)
-            authHost = referer.protocol+"//"+referer.host;
-        
         let options = {
-            url: authHost + this.options.authEndpoint,
+            url: this.authHost(socket) + this.options.authEndpoint,
             form: { channel_name: data.channel },
             headers: (data.auth && data.auth.headers) ? data.auth.headers : {},
             rejectUnauthorized: false
@@ -47,9 +41,26 @@ export class PrivateChannel {
      *
      * @return {string}
      */
-    protected authHost(): string {
-        return (this.options.authHost) ?
+    protected authHost(socket: any): string {
+        let referer: Object = url.parse(socket.request.headers.referer);
+        let authHostSelected: string = 'http://localhost';
+        let authHosts: any = (this.options.authHost) ?
             this.options.authHost : this.options.host;
+        
+        if(typeof authHosts === "string")
+            authHosts = [authHosts];
+        
+        for(let authHost of authHosts)
+        {
+            authHostSelected = authHost;
+            if(referer.hostname.substr(referer.hostname.indexOf('.')) === authHostSelected || referer.protocol + "//" + referer.host === authHostSelected || referer.host === authHostSelected)
+            {
+                authHostSelected = referer.protocol+"//"+referer.host;
+                break;
+            }
+        }
+
+        return authHostSelected;
     }
 
     /**