Make toolbar layout flexible

1. Do not wrap toolbar buttons in small screen
2. Show title as wide as possible in large screen

Author: ohtake

src/Styles.js

@@ -125,24 +125,25 @@ const styles = {
         top             : 0,
         right           : 0,
         height          : toolbarHeight,
+        display         : 'flex',
+        justifyContent  : 'space-between',
     },
     toolbarSide: {
-        lineHeight : toolbarHeight,
-        position   : 'absolute',
-        top        : 0,
-        bottom     : 0,
-        margin     : 0,
-        maxWidth   : '48%',
+        height : toolbarHeight,
+        margin: 0,
+        padding: 0,
     },
     toolbarLeftSide: {
         paddingLeft  : '20px',
         paddingRight : 0,
-        left         : 0,
+        flex         : '0 1 auto',
+        overflow     : 'hidden',
+        textOverflow : 'ellipsis',
     },
     toolbarRightSide: {
         paddingLeft  : 0,
         paddingRight : '20px',
-        right        : 0,
+        flex         : '0 0 auto',
     },
     toolbarItem: {
         display       : 'inline-block',