Added a unit test for notifications count

This unit tests fail on my machine:

unit.framework.AssertionFailedError: expected:<2> but was:<1>
at io.realm.NotificationsTest.testNotifications(NotificationsTest.java:98)
at java.lang.reflect.Method.invokeNative(Native Method)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)