update HISTORY with related issues

Author: tilomitra

HISTORY.md

@@ -12,12 +12,13 @@ NEXT
 ### Grids
 
 * __[!]__ Removed `.pure-g-r` from core, in favor of a mobile-first responsive
-  grid system. To use the mobile-first grid system, you need to pull in
-  `pure.css`, along with `grids-responsive.css`:
+  grid system. ([#24][], [#267][])
+
+  To use the mobile-first grid system, you need to pull in `pure.css`, along with `grids-responsive.css`:
 
     ```html
-    <link rel="stylesheet" href="http://yui.yahooapis.com/pure/0.5.0-rc1/pure-min.css">
-    <link rel="stylesheet" href="http://yui.yahooapis.com/pure/0.5.0-rc1/grids-responsive-min.css">
+    <link rel="stylesheet" href="http://yui.yahooapis.com/pure/0.5.0-rc-1/pure-min.css">
+    <link rel="stylesheet" href="http://yui.yahooapis.com/pure/0.5.0-rc-1/grids-responsive-min.css">
     ```
 
   Find out more about the new grid system at [http://purecss.io/grids/][Grids].
@@ -27,6 +28,8 @@ NEXT
 * Switched cell padding in Tables from `px` to `em` units, and also increased
   the amount of padding to `padding: 0.5em 1em`.
 
+[#24]: https://github.com/yui/pure/issues/24
+[#267]: https://github.com/yui/pure/pull/267
 [Grids]: http://purecss.io/grids/
 
 0.4.2 (2014-02-13)