added getStepCountForToday method docs

README.md

@@ -12,6 +12,7 @@ A React Native bridge module for interacting with [Apple HealthKit] data.
     * [Methods](#methods)
       * [isAvailable](#isavailable)
       * [initHealthKit](#inithealthkit)
+      * [getStepCountForToday](#getstepcountfortoday)
       * [getLatestWeight](#getlatestweight)
       * [saveWeight](#saveweight)
       * [getLatestHeight](#getlatestheight)
@@ -159,6 +160,20 @@ AppleHealthKit.initHealthKit(healthKitOptions: object, (err: string, res: object
 
 ___
 
+
+#### **`getStepCountForToday`**
+get the the aggregated total steps for the current day starting and ending at midnight
+```javascript
+AppleHealthKit.getStepCountForToday(null, (err: Object, steps: number) => {
+    if(this._handleHealthKitError(err, 'getStepCountForToday')){
+        return;
+    }
+    // use steps...
+});
+```
+
+___
+
 #### **`getLatestWeight`**
 get the most recent weight value
 ```javascript