replace implicit this == window with explicit binding

app/assets/javascripts/u2f/register.js

@@ -95,4 +95,4 @@
     return U2FRegister;
   })();
-}).call(this);
+}).call(window);

app/assets/javascripts/u2f/util.js

@@ -9,4 +9,4 @@
     return U2FUtil;
   })();
-}).call(this);
+}).call(window);

app/assets/javascripts/users/calendar.js

@@ -221,4 +221,4 @@
     return Calendar;
   })();
-}).call(this);
+}).call(window);

app/assets/javascripts/users_select.js

@@ -432,4 +432,4 @@
     return UsersSelect;
   })();
-}).call(this);
+}).call(window);

app/assets/javascripts/zen_mode.js

@@ -94,4 +94,4 @@ require('mousetrap/plugins/pause/mousetrap-pause');
     return ZenMode;
   })();
-}).call(this);
+}).call(window);