Adding hide scroll indicator props (#84)

* adding hide scroll indicator props

* proptypes and readme

Author: junyuanxue

Diff for: README.md

@@ -31,6 +31,8 @@ npm i react-native-sortable-list --save
 - **contentContainerStyle?** (Object, Array) these styles will be applied to the inner scroll view content container
 - **innerContainerStyle?** (Object, Array) these styles will be applied to the inner scroll view content container, excluding the header and footer
 - **horizontal?** (boolean) when true, the SortableList's children are arranged horizontally in a row instead of vertically in a column. The default value is false.
+- **showsVerticalScrollIndicator** (boolean) when false, the vertical scroll indicator will not be visible. The default value is true.
+- **showsHorizontalScrollIndicator** (boolean) when false, the horizontal scroll indicator will not be visible. The default value is true.
 - **sortingEnabled?** (boolean) when false, rows are not sortable. The default value is true.
 - **scrollEnabled?** (boolean) when false, the content does not scrollable. The default value is true.
 - **manuallyActivateRows?** (bool) whether you intend to use the `toggleRowActive` method to activate a row or use the out of box solution.

Diff for: src/SortableList.js

@@ -23,6 +23,8 @@ export default class SortableList extends Component {
     sortingEnabled: PropTypes.bool,
     scrollEnabled: PropTypes.bool,
     horizontal: PropTypes.bool,
+    showsVerticalScrollIndicator: PropTypes.bool,
+    showsHorizontalScrollIndicator: PropTypes.bool,
     refreshControl: PropTypes.element,
     autoscrollAreaSize: PropTypes.number,
     rowActivationTime: PropTypes.number,
@@ -41,7 +43,9 @@ export default class SortableList extends Component {
     sortingEnabled: true,
     scrollEnabled: true,
     autoscrollAreaSize: 60,
-    manuallyActivateRows: false
+    manuallyActivateRows: false,
+    showsVerticalScrollIndicator: true,
+    showsHorizontalScrollIndicator: true
   }
 
   /**
@@ -180,7 +184,7 @@ export default class SortableList extends Component {
   }
 
   render() {
-    let {contentContainerStyle, innerContainerStyle, horizontal, style} = this.props;
+    let {contentContainerStyle, innerContainerStyle, horizontal, style, showsVerticalScrollIndicator, showsHorizontalScrollIndicator} = this.props;
     const {animated, contentHeight, contentWidth, scrollEnabled} = this.state;
     const containerStyle = StyleSheet.flatten([style, {opacity: Number(animated)}])
     innerContainerStyle = [
@@ -205,6 +209,8 @@ export default class SortableList extends Component {
           contentContainerStyle={contentContainerStyle}
           scrollEventThrottle={2}
           scrollEnabled={scrollEnabled}
+          showsHorizontalScrollIndicator={showsHorizontalScrollIndicator}
+          showsVerticalScrollIndicator={showsVerticalScrollIndicator}
           onScroll={this._onScroll}>
           {this._renderHeader()}
           <View style={innerContainerStyle}>