Fixed error where webpage crashes if the Redux dev extension is not installed.

src/index.js

@@ -17,17 +17,16 @@ import  amber  from 'material-ui/colors/amber';
 import red from 'material-ui/colors/red';
 import green from 'material-ui/colors/green';
 // Create a history of your choosing (we're using a browser history in this case)
-const history = createHistory()
+const history = createHistory();
 const extension = window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__();
 if(extension){
     const enhance = compose(
         applyMiddleware(ReduxThunk,routerMiddleware(history))
-        ,extension)
+        ,extension);
 }
 const enhance = compose(
-        applyMiddleware(ReduxThunk,routerMiddleware(history))
-        ,extension)
-const store = createStore(reducers,enhance)
+        applyMiddleware(ReduxThunk,routerMiddleware(history)));
+const store = createStore(reducers,enhance);
 
 const theme = createMuiTheme({
     palette: {primary:blue,secondary:green,warn:amber,error:red,type:'light'}