Ledger warning (#709)

* Ledger HTTPS warning.

* Missed colon.

common/components/WalletDecrypt/components/LedgerNano.tsx

@@ -43,6 +43,17 @@ export class LedgerNanoSDecrypt extends Component<Props, State> {
     const { dPath, publicKey, chainCode, error, isLoading, showTip } = this.state;
     const showErr = error ? 'is-showing' : '';
 
+    if (window.location.protocol !== 'https:') {
+      return (
+        <div className="LedgerDecrypt">
+          <div className="alert alert-danger">
+            Unlocking a Ledger hardware wallet is only possible on pages served over HTTPS. You can
+            unlock your wallet at <a href="https://myetherwallet.com">MyEtherWallet.com</a>
+          </div>
+        </div>
+      );
+    }
+
     return (
       <div className="LedgerDecrypt">
         {showTip && (