Merge pull request #33 from ESA2012/master

fix multiple instances creation of mFingerprintIdentify

Author: hieuvp

android/src/main/java/com/hieuvp/fingerprint/ReactNativeFingerprintScannerModule.java

@@ -41,6 +41,9 @@ public void onHostDestroy() {
     }
 
     private FingerprintIdentify getFingerprintIdentify() {
+        if (mFingerprintIdentify != null) {
+            return mFingerprintIdentify;
+        }
         mReactContext.addLifecycleEventListener(this);
         mFingerprintIdentify = new FingerprintIdentify(getCurrentActivity(),
                 new FingerprintIdentifyExceptionListener() {