rename fill attribute

Summary:
We were using `fill={true}` as an attribute to make flexbox containers fill the entire available space.

However, `fill` is an HTML attribute (see: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill) This caused warnings printed to the console.

This diff renames the attribute to `grow` with is also more in line with the Flexbox terminology.

Reviewed By: priteshrnandgaonkar

Differential Revision: D10488389

fbshipit-source-id: ed8553c6203cdf6df94d26c731164ecec4c9fbd2

src/App.js

@@ -49,7 +49,7 @@ export class App extends React.Component<Props> {
   }
   render() {
     return (
-      <FlexColumn fill={true}>
+      <FlexColumn grow={true}>
         <TitleBar />
         {this.props.bugDialogVisible && (
           <BugReporterDialog
@@ -59,7 +59,7 @@ export class App extends React.Component<Props> {
             }}
           />
         )}
-        <FlexRow fill={true}>
+        <FlexRow grow={true}>
           {this.props.leftSidebarVisible && <MainSidebar />}
           {this.props.selectedDevice ? (
             <PluginContainer logger={this.props.logger} />