URL Changes (dexlab-io#78)

* Created a new method of the Dashboard component, which changes the
  URL of the current page according to the active tab
* Called the new method from the tab change handlers for desktop and mobile

src/pages/Dashboard/index.js

@@ -89,6 +89,15 @@ class Dashboard extends Component {
     this.confetti();
   }
 
+  setUrl = nextTab => {
+    if (nextTab === 'tip') {
+      window.history.replaceState({}, '', '/address/' + this.state.pos.address + '/tip');
+    }
+    else {
+      window.history.replaceState({}, '', '/address/' + this.state.pos.address);
+    }
+  }
+
   handleNavItemChange = activeTab => {
     // eslint-disable-next-line
     const currentTab = this.state.activeTab;
@@ -100,8 +109,14 @@ class Dashboard extends Component {
       this.setState({ totalAmount: '0' });
     }
     this.setState({ activeTab, lastTab: currentTab });
+    this.setUrl(nextTab);
   };
 
+  handleTabChange = nextTab => {
+    this.setState({ activeTab: nextTab });
+    this.setUrl(nextTab);
+  }
+
   onCloseTip = () => {
     this.handleNavItemChange(this.state.lastTab);
   };

src/pages/Dashboard/mobile.view.js

@@ -21,7 +21,7 @@ export default function() {
       <div className="container is-fluid">
         <NavTabs
           activeTab={activeTab}
-          onChange={tab => this.setState({ activeTab: tab })}
+          onChange={this.handleTabChange}
         />
         {pos.address ? (
           <div>