refactor of codes and validation

Author: mikelis135

raveandroid/src/main/java/com/flutterwave/raveandroid/data/SharedPrefsRequestImpl.java

@@ -4,7 +4,6 @@
 import android.content.SharedPreferences;
 import android.util.Log;
 
-import com.flutterwave.raveandroid.RaveConstants;
 import com.flutterwave.raveandroid.Utils;
 import com.google.gson.Gson;
 import com.google.gson.reflect.TypeToken;
@@ -13,6 +12,8 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import static com.flutterwave.raveandroid.RaveConstants.RAVEPAY;
+
 /**
  * Created by hamzafetuga on 25/07/2017.
  */