clean four MapView lint warnings

Summary:
clean four MapView lint warnings.
Closes https://github.com/facebook/react-native/pull/4778

Reviewed By: svcscm

Differential Revision: D2759161

Pulled By: androidtrunkagent

fb-gh-sync-id: c5b028d0400c5084436d636d3bf9a0072fa09571

Libraries/Components/MapView/MapView.js

@@ -18,12 +18,8 @@ var Platform = require('Platform');
 var RCTMap = require('UIManager').RCTMap;
 var RCTMapConstants = RCTMap && RCTMap.Constants;
 var React = require('React');
-var ReactNativeViewAttributes = require('ReactNativeViewAttributes');
 var View = require('View');
 
-var deepDiffer = require('deepDiffer');
-var insetsDiffer = require('insetsDiffer');
-var merge = require('merge');
 var processColor = require('processColor');
 var resolveAssetSource = require('resolveAssetSource');
 var requireNativeComponent = require('requireNativeComponent');