Changed Android Support version from 27.1.0 to 25.4.0 (#20)

Author: Bruno Ferrari

library/src/androidTest/java/com/xmartlabs/xmartrecyclerview/common/RecyclerViewAssertions.java

@@ -11,7 +11,7 @@
 
 import java.util.Locale;
 
-import static android.support.v4.util.Preconditions.checkNotNull;
+import static android.support.test.internal.util.Checks.checkNotNull;
 
 public class RecyclerViewAssertions {
   public static Matcher<View> countIs(int count) {

versions.gradle

@@ -6,7 +6,7 @@ ext {
     targetSdkVersion = 27
 
     libraryVersion = [
-        androidSupport: '27.1.0',
+        androidSupport: '25.4.0',
         espresso: '3.0.1',
         junit: '4.12',
         stream: '1.1.6',