Add API class

- Secure token based on username/password

pubspec.yaml

@@ -23,6 +23,7 @@ dependencies:
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^0.1.2
+  http: ^0.12.0+2
 
 dev_dependencies:
   flutter_test: