title: FlutterFirebaseCorePlugin.java uses or overrides a deprecated API
body: <p>Ok so I run my program without importing firebase core, firebase auth and cloud firestore, and my code runs just fine but I register my app with firebase and it still runs fine but as soon as I import <code>Firebase_auth</code>, <code>Firebase_core</code> and <code>cloud_Firestore</code>... I get the following error</p>
  <pre><code>Note: C:\appflutter\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_core-0.7.0\android\src\main\java\io\flutter\plugins\firebase\core\FlutterFirebaseCorePlugin.java uses or overrides a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  Note: C:\appflutter\flutter\.pub-cache\hosted\pub.dartlang.org\cloud_firestore-0.16.0\android\src\main\java\io\flutter\plugins\firebase\firestore\streamhandler\TransactionStreamHandler.java uses unchecked or unsafe operations.
  Note: Recompile with -Xlint:unchecked for details.
  D8: Cannot fit requested classes in a single dex file (# methods: 89543 &gt; 65536)
  com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives: 
  The number of method references in a .dex file cannot exceed 64K.
  </code></pre>
  <p>Please help me.</p>