Remove image replacement helper class .ir

This class was removed because it doesn't provide enough use
cases within modern web development. Cases are mostly handled
indiviually by developers.

Reference #1472.
Closes #1475.

CHANGELOG.md

@@ -1,5 +1,6 @@
 ### HEAD
 
+* Remove image replacement helper class `.ir`
 * Update to Modernizr 2.7.0.
 * Update to Apache Server Configs 2.0.0.
 * Add vertical centering for `svg` ([#1453](https://github.com/h5bp/html5-boilerplate/issues/1453)).

css/main.css

@@ -118,23 +118,6 @@ textarea {
    Helper classes
    ========================================================================== */
 
-/*
- * Image replacement
- */
-
-.ir {
-    background-color: transparent;
-    border: 0;
-    overflow: hidden;
-}
-
-.ir:before {
-    content: "";
-    display: block;
-    width: 0;
-    height: 150%;
-}
-
 /*
  * Hide from both screenreaders and browsers: h5bp.com/u
  */
@@ -251,7 +234,6 @@ textarea {
      * Don't show links for images, or javascript/internal links
      */
 
-    .ir a:after,
     a[href^="javascript:"]:after,
     a[href^="#"]:after {
         content: "";

doc/css.md

@@ -38,13 +38,6 @@ You are free to modify or add to these base styles as your project requires.
 
 ## Common helpers
 
-#### `.ir`
-
-Add the `.ir` class to any element you are applying image-replacement to. When
-replacing an element's content with an image, make sure to also set a specific
-`background-image: url(pathtoimage.png);`, `width`, and `height` so that your
-replacement image appears.
-
 #### `.hidden`
 
 Add the `.hidden` class to any elements that you want to hide from all