fix(mixpanel): Make eventProperties optional (#501)

* fix(mixpanel): Make eventProperties optional

* style(mixpanel): Match editorconfig

src/plugins/mixpanel.ts

@@ -1,5 +1,8 @@
-import {Plugin, Cordova, CordovaProperty} from './plugin';
+import { Cordova, CordovaProperty, Plugin } from './plugin';
+
 declare var mixpanel: any;
+
+
 /**
  * @name Mixpanel
  * @description
@@ -28,73 +31,73 @@ export class Mixpanel {
    * @returns {Promise<any>}
    */
   @Cordova()
-  static alias(aliasId: string, originalId: string): Promise<any> {return; }
+  static alias(aliasId: string, originalId: string): Promise<any> { return; }
 
   /**
    *
    * @returns {Promise<any>}
    */
   @Cordova()
-  static distinctId(): Promise<any> {return; }
+  static distinctId(): Promise<any> { return; }
 
   /**
    *
    */
   @Cordova()
-  static flush(): Promise<any> {return; }
+  static flush(): Promise<any> { return; }
 
   /**
    *
    * @param distinctId {string}
    * @returns {Promise<any>}
    */
   @Cordova()
-  static identify(distinctId): Promise<any> {return; }
+  static identify(distinctId): Promise<any> { return; }
 
   /**
    *
    * @param token {string}
    * @returns {Promise<any>}
    */
   @Cordova()
-  static init(token: string): Promise<any> {return; }
+  static init(token: string): Promise<any> { return; }
 
   /**
    *
    * @param superProperties
    * @returns {Promise<any>}
    */
   @Cordova()
-  static registerSuperProperties(superProperties: any): Promise<any> {return; }
+  static registerSuperProperties(superProperties: any): Promise<any> { return; }
 
   /**
    *
    * @returns {Promise<any>}
    */
   @Cordova()
-  static reset(): Promise<any> {return; }
+  static reset(): Promise<any> { return; }
 
   /**
    *
    * @param eventName
    * @param eventProperties
    */
   @Cordova()
-  static track(eventName: string, eventProperties: any): Promise<any> {return; }
+  static track(eventName: string, eventProperties?: any): Promise<any> { return; }
 
   /**
    *
    * @returns {Promise<any>}
    */
   @Cordova()
-  static showSurvey(): Promise<any> {return; }
+  static showSurvey(): Promise<any> { return; }
 
   /**
    *
    * @returns {MixpanelPeople}
    */
   @CordovaProperty
-  static get people(): MixpanelPeople {return mixpanel.people; };
+  static get people(): MixpanelPeople { return mixpanel.people; };
 
 }
 /**