docs(guide/Conceptual Overview): use exchangeratesapi.io

docs/content/guide/concepts.ngdoc

@@ -186,7 +186,7 @@ Right now, the `InvoiceController` contains all logic of our example. When the a
 is a good practice to move view-independent logic from the controller into a
 <a name="service">{@link services service}</a>, so it can be reused by other parts
 of the application as well. Later on, we could also change that service to load the exchange rates
-from the web, e.g. by calling the [Fixer.io](http://fixer.io) exchange rate API, without changing the controller.
+from the web, e.g. by calling the [exchangeratesapi.io](https://exchangeratesapi.io) exchange rate API, without changing the controller.
 
 Let's refactor our example and move the currency conversion into a service in another file:
 
@@ -300,7 +300,7 @@ to something shorter like `a`.
 
 ## Accessing the backend
 
-Let's finish our example by fetching the exchange rates from the [Fixer.io](http://fixer.io) exchange rate API.
+Let's finish our example by fetching the exchange rates from the [exchangeratesapi.io](https://exchangeratesapi.io) exchange rate API.
 The following example shows how this is done with AngularJS:
 
 <example name="guide-concepts-3" ng-app-included="true">
@@ -331,7 +331,7 @@ The following example shows how this is done with AngularJS:
         };
 
         var refresh = function() {
-          var url = 'https://api.fixer.io/latest?base=USD&symbols=' + currencies.join(",");
+          var url = 'https://api.exchangeratesapi.io/latest?base=USD&symbols=' + currencies.join(",");
           return $http.get(url).then(function(response) {
             usdToForeignRates = response.data.rates;
             usdToForeignRates['USD'] = 1;