removed mixin for text-sr and text-hide, replaced with extend

cms/static/sass/_base.scss

@@ -581,7 +581,7 @@ p, ul, ol, dl {
 
 // misc
 hr.divide {
-  @include text-sr();
+  @extend text-sr;
 }
 
 .item-details {
@@ -832,7 +832,7 @@ hr.divide {
 
 // basic utility
 .sr {
-  @include text-sr();
+  @extend text-sr;
 }
 
 .fake-link {
@@ -885,7 +885,7 @@ body.js {
       text-align: center;
 
       .label {
-        @include text-sr();
+        @extend text-sr;
       }
 
       .ss-icon {

cms/static/sass/elements/_header.scss

@@ -67,7 +67,7 @@
   padding-right: ($baseline*0.75);
 
   a {
-    @include text-hide();
+    @extend text-hide;
     display: block;
     width: 164px;
     height: 32px;

cms/static/sass/elements/_system-feedback.scss

@@ -442,7 +442,7 @@
     }
 
     .copy p {
-      @include text-sr();
+      @extend text-sr;
     }
   }
 }
@@ -597,7 +597,7 @@
     text-align: center;
 
     .label {
-      @include text-sr();
+      @extend text-sr;
     }
 
     .icon {

cms/static/sass/views/_checklists.scss

@@ -23,7 +23,7 @@ body.course.checklists {
 
     // visual status
     .viz-checklist-status {
-      @include text-hide();
+      @extend text-hide;
       @include size(100%,($baseline/4));
       position: relative;
       display: block;
@@ -40,7 +40,7 @@ body.course.checklists {
         background: $green;
 
         .int {
-          @include text-sr();
+          @extend text-sr;
         }
       }
     }

cms/static/sass/views/_index.scss

@@ -72,7 +72,7 @@ body.index {
       }
 
       .logo {
-        @include text-hide();
+        @extend text-hide;
         position: relative;
         top: 3px;
         display: inline-block;