Remove unnecessary vendor prefixes

Firefox ESR is currently at Firefox 31, which doesn't require box-sizing
prefixes.

Fix necolas#400

README.md

@@ -34,7 +34,7 @@ library code.
 
 * Google Chrome (latest)
 * Mozilla Firefox (latest)
-* Mozilla Firefox 4
+* Mozilla Firefox ESR
 * Opera (latest)
 * Apple Safari 6+
 * Internet Explorer 8+

normalize.css

@@ -210,7 +210,6 @@ figure {
  */
 
 hr {
-  -moz-box-sizing: content-box;
   box-sizing: content-box;
   height: 0;
 }
@@ -351,15 +350,12 @@ input[type="number"]::-webkit-outer-spin-button {
 
 /**
  * 1. Address `appearance` set to `searchfield` in Safari and Chrome.
- * 2. Address `box-sizing` set to `border-box` in Safari and Chrome
- *    (include `-moz` to future-proof).
+ * 2. Address `box-sizing` set to `border-box` in Safari and Chrome.
  */
 
 input[type="search"] {
   -webkit-appearance: textfield; /* 1 */
-  -moz-box-sizing: content-box;
-  -webkit-box-sizing: content-box; /* 2 */
-  box-sizing: content-box;
+  box-sizing: content-box; /* 2 */
 }
 
 /**