修复了android下list view无粘滞效果。review by 孙凯。

@@ -316,7 +316,7 @@ var ListView = React.createClass({
       renderScrollComponent: props => <ScrollView {...props} />,
       scrollRenderAheadDistance: DEFAULT_SCROLL_RENDER_AHEAD,
       onEndReachedThreshold: DEFAULT_END_REACHED_THRESHOLD,
-      stickySectionHeadersEnabled: Platform.OS === 'ios',
+      stickySectionHeadersEnabled: true,
       stickyHeaderIndices: [],
     };
   },

@@ -180,7 +180,7 @@ type Props<SectionT> = RequiredProps<SectionT>
 
 const defaultProps = {
   ...VirtualizedSectionList.defaultProps,
-  stickySectionHeadersEnabled: Platform.OS === 'ios',
+  stickySectionHeadersEnabled: true,
 };
 
 type DefaultProps = typeof defaultProps;