add ie7 inline block mixin and add ability to center pagination

lib/pagination.less

@@ -5,7 +5,8 @@
   height: @baseLineHeight * 2;
   margin: @baseLineHeight 0;
   ul {
-    float: left;
+    display: inline-block;
+    .ie7-inline-block();
     margin: 0;
     border: 1px solid #ddd;
     border: 1px solid rgba(0,0,0,.15);
@@ -37,4 +38,9 @@
   .next a {
     border: 0;
   }
+
+  // Centered
+  &.centered {
+    text-align: center;
+  }
 }