start to support live mode (#73)

1. add a liveMode flag to config, when liveMode is set, the timer
will keep running even though all the actions casted
2. add a public method addEvent, which will cast newly added event
in sync
3. move mouse in sync mode with the latest position info

typings/replay/index.d.ts

@@ -22,6 +22,7 @@ export declare class Replayer {
     play(timeOffset?: number): void;
     pause(): void;
     resume(timeOffset?: number): void;
+    addEvent(event: eventWithTime): void;
     private setupDom;
     private handleResize;
     private getDelay;

typings/types.d.ts

@@ -192,6 +192,7 @@ export declare type playerConfig = {
     showWarning: boolean;
     showDebug: boolean;
     blockClass: string;
+    liveMode: boolean;
 };
 export declare type playerMetaData = {
     totalTime: number;