title: Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables
body: <p>I am using Room With RxJava2. I added a column in my table so I am migrating to new version. I have changed my Database version to 2.</p>
  
  <p>Following is my migration code</p>
  
  <pre><code>static final Migration MIGRATION_1_2 = new Migration(1, 2) {
      @Override
      public void migrate(SupportSQLiteDatabase database) {
          database.execSQL("ALTER TABLE users "
          +"ADD COLUMN address String");
  
      }
  };
  
  AppDatabase db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, DB_NAME)
  .addMigrations(MIGRATION_1_2)
  .build();
  </code></pre>
  
  <p>If you want to see the full code,
  I am refering to this example on Github, it does not have the migration code</p>
  
  <pre><code>https://github.com/alahammad/RoomSample
  </code></pre>
  
  <p>I am following the steps described in the documentation but still my app crashes.</p>
  
  <p>Error Logs</p>
  
  <pre><code>Process: demo.karaoke.sensibol.com.roomrajava2, PID: 13655
      io.reactivex.exceptions.OnErrorNotImplementedException: A migration from 1 to 2 is necessary. Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables.
          at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
          at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
          at io.reactivex.internal.operators.maybe.MaybeCallbackObserver.onError(MaybeCallbackObserver.java:83)
          at io.reactivex.internal.operators.maybe.MaybeObserveOn$ObserveOnMaybeObserver.run(MaybeObserveOn.java:99)
          at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:109)
          at android.os.Handler.handleCallback(Handler.java:815)
          at android.os.Handler.dispatchMessage(Handler.java:104)
          at android.os.Looper.loop(Looper.java:194)
          at android.app.ActivityThread.main(ActivityThread.java:5643)
          at java.lang.reflect.Method.invoke(Native Method)
          at java.lang.reflect.Method.invoke(Method.java:372)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:960)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
       Caused by: java.lang.IllegalStateException: A migration from 1 to 2 is necessary. Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables.
          at android.arch.persistence.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:82)
          at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:118)
          at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:256)
          at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
          at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:93)
          at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:54)
          at android.arch.persistence.room.RoomDatabase.query(RoomDatabase.java:193)
          at demo.karaoke.sensibol.com.roomrajava2.UserDao_Impl$4.call(UserDao_Impl.java:137)
          at demo.karaoke.sensibol.com.roomrajava2.UserDao_Impl$4.call(UserDao_Impl.java:135)
          at io.reactivex.internal.operators.maybe.MaybeFromCallable.subscribeActual(MaybeFromCallable.java:46)
          at io.reactivex.Maybe.subscribe(Maybe.java:3749)
          at io.reactivex.internal.operators.maybe.MaybeSubscribeOn$SubscribeTask.run(MaybeSubscribeOn.java:54)
          at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452)
          at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)
          at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)
          at java.util.concurrent.FutureTask.run(FutureTask.java:237)
          at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
          at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
          at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
          at java.lang.Thread.run(Thread.java:818)
  </code></pre>