bump version, add test for onStartCallback

Author: inorganik

README.md

@@ -69,7 +69,7 @@ interface CountUpOptions {
   scrollSpyDelay?: number; // delay (ms) after target comes into view
   scrollSpyOnce?: boolean; // run only once
   onCompleteCallback?: () => any; // gets called when animation completes
-  onStartCallback?: () => any; // gets called when animation start
+  onStartCallback?: () => any; // gets called when animation starts
   plugin?: CountUpPlugin; // for alternate animations
 }
 ```
@@ -90,12 +90,6 @@ Pass options:
 const countUp = new CountUp('targetId', 5234, options);
 ```
 
-with optional start callback:
-
-```js
-const countUp = new CountUp('targetId', 5234, { onStartCallback: someMethod });
-```
-
 with optional complete callback:
 
 ```js

dist/countUp.js

@@ -15,7 +15,7 @@ var CountUp = /** @class */ (function () {
         var _this = this;
         this.endVal = endVal;
         this.options = options;
-        this.version = '2.7.1';
+        this.version = '2.8.0';
         this.defaults = {
             startVal: 0,
             decimalPlaces: 0,